*************************** ** THE GEM MESSENGER ** *************************** Volume 12, Number 27 August 5, 2002 ------------------------------------------------------------ GEM 2002 Workshop Report of WG 1 of the MI Coupling Campaign ------------------------------------------------------------ From: Bill Peterson GEM Summer Workshop 2002 June 24-27, 2002, Telluride, Colorado Report of WG 1 of the MI coupling campaign Magnetosphere-Ionosphere Mass Transfer W.K. Peterson and T.E. Moore SUMMARY WG 1 on mass exchanges invited a tutorial speaker, organized three sessions and participated in two others. A summary of these sessions is given below. Perhaps the most significant outcomes of the discussions during the week were: 1) The intense interest in all participants in unraveling the role played by mass outflow from the magnetosphere to the ionosphere. 2) The variety and quality of new data and reanalysis of old data that is now available: Perhaps the best examples of reanalysis of old data were the solar cycle summaries of outflow obtained from the SMS instrument on Akebono presented by Drs. Yau and Abe which are discussed below. The best examples of new data were the Cluster data obtained in the tail and the plasmaspheric images. Some of the best examples of empirical results ready for application to global simulations were reported from the FAST data set by Bob Strangeway. 3) The difficulty of achieving a consensus on a way to organize a challenge to bring observations and modeling together (see below). In view of point 3, we propose to select a small number of intervals for which we will ask for observers and modelers to characterize as completely as possible: a) Energy transfer from the magnetosphere to the ionosphere, in all forms b) The state of the topside ionosphere, plasmasphere, and plasma sheet c) The outflow of ionospheric plasma in response to the inputs. d) System behavior as modeled with/without the ionospheric mass transfer. We plan to organize a discussion to pick at least two intervals in a pre- Fall AGU GEM session and challenge observers to come to the 2003 GEM meeting prepared to characterize the ionosphere and it's contribution to the magnetosphere. The best ion mass spectrometer data from FAST, Polar, and Akebono are available in 1997, suggesting that one of the intervals should be in 1997. The recent launch of TIMED and availability of data from IMAGE and Cluster suggests that one of the intervals should be after February, 2002. SESSION SUMMARIES Tutorial: Prof. Andrew Yau, University of Calgary, Canada, presented an overview of the current state of our understanding of the processes responsible for mass outflow and the consequences in the magnetosphere that follow. He made a clear distinction between thermal (i.e. polar wind) and energetic ion outflow. He presented the results of analysis of more than a solar cycle¹s data on the flux of ion outflow from the Canadian SMS instrument on the Japanese Akebono (Exos -D) satellite. In particular he presented the results of a statistical study showing significant positive correlation between O+ ion outflow and Solar Activity as paramerized by the F10.7 Index. The H+ correlation with F10.7 was slightly negative, i.e. more H+ outflow during periods of low F10.7. He also showed a stronger correlation between ion outflow and the solar wind pressure than with magnetic activity as parameterized by the Kp index. The results of this study will appear soon in a JGR paper by Cully et al. Dr. Yau also presented results of simple models of the transport of ionospheric ions to the plasma sheet showing how changes in the large-scale electric field dramatically affect the transport of ionospheric plasma to the plasma sheet. Session on Plasmaspheric Plumes: Dr. Yi-Jiun Su ­ Presented an overview of her work with a solar cycles worth of plasmaspheric observations derived from low energy LANL ion data. She also showed that observations made by the Millstone radar observations agree with the LANL geosynchronous observations. In particular she noted that the both the plasmaspheric refilling rate and speed of convection increase with magnetic activity (i.e. with Kp). Dr. Jerry Goldstein ­ Presented various examples of imaging and motions of plasmasphere obtained from the EUV instrument on the IMAGE satellite. He noted both the creation of plasmaspheric plumes and their dynamics. He demonstrated that Kp=5 is enough to get a nice plume. If convection continues the EUV images clearly show the plasmasphere wrapping up. Dr. Maria Spasojevic ­ Also presented images of the plasmasphere from the EUV imager on IMAGE. She made same points much more clearly because she explicitly presented and compared with in-situ density observations from the IMAGE RPI instrument. Dr. Denis Gallagher ­ Presented a compilation of movies of time histories of images from the EUV imager data. These movies showed that density rises at low L when it drops off at high L. At the time of geomagnetic activity the moves show that the entire plasmasphere is compressed, rather than displaced, or pushed down into ionosphere. Dr. Peterson commented that the movies would have been much more informative if they included index plots showing geomagnetic activity and estimates of the convection electric field derived from the data. Dr. John Foster ­ Presented a comprehensive series of observations of enhanced density features in the topside ionosphere extending from low latitutes into the polar cap. He showed that these features are the direct signature the stripping off the plasmaspheric plumes at the onset of strongly enhanced convection. He showed examples of density enhancements extending from Florida to Alberta when plumes are created. He also presented evidence of plasma enhancements in the polar cap associated with these events. Dr. Mark Engebretson - Presented ULF Wave observations made from the Antarctic and the Polar satellite. He showed that there was a class of waves occurring on isolated L shells that energize thermal He and H up into 100 eV range where they are detected by the TIMAS energetic ion mass spectrometer on Polar. He identified a potential source of free energy for the ULF waves in the keV ion data. Dr. Bill Peterson ­ Presented observations of energized thermal plasmaspheric He+ inside and outside of the dayside magnetopause obtained from the Polar satellite in March 2002. In one case both the TIMAS and CAMMICE instruments saw He+ in the keV energy range. In another case, TIDE data was presented that clearly resolved the density and temperature of the energized He+ component. Dr. Peterson noted that the combination of motion of the magnetic field in response to ULF pulsations and compression of the magnetosphere make the routine detection of very low (i.e. ~ 2 or 3 cm-3) He+ ion densities possible) He noted that these data can be used to complement and extend the global images presented by Drs. Goldstein, Spasojevic, and Gallagher Dr. Tom Moore ­ extended the discussion of low energy ions observations at the subsolar magnetopause most all the time. He pointed out they vary tremendously in density, corresponding to the variation from partially to fully filled flux tubes. Discussion ­ There was a vigorous discussion of all sorts of implications of dense ionospheric plasma being at the dayside magnetopause routinely, especially if variable in density. We are looking forward to more quantitative presentations on this topic at future meetings. Session on Auroral Outflow Contributions to Magnetospheric Plasma Dr. Robert Winglee ­ Discussed the implications of some recent simulations made with this unique multi-fluid MHD code. He noted that most nightside and flank H+ from the ionosphere enter the plasma sheet in the event modeled, which had conditions of very strong activity characteristic of a large storm. In this case, O+ from the dayside cusp region is energized so much that it is lost downstream without entering the plasmasheet. He also noted that the cross polar cap potential and associated cross tail electric field results in significant energization in his codes. Dr. Steve Mende ­ Presented observations of the substorm surge and associated ion outflow. The images were obtained from the IMAGE/WIC camera and the ion observations from FAST. He suggests that the surge region is associated with intense H+ outflow. He emphasized that the images put the location of the surge well equatorward of the poleward edge of auroral emissions. These observations and suggestions were amplified in the Tutorial talk given the following day by Dr. Robert McFadden. The suggestion made by Dr. Mende, McFadden and others at the conference is that the ions in the surge are accelerated by an ³Alvenic² process that is different from the processes associated with the downward and upward current regions. Dr. Lila Andersson ­ Presented preliminary results from a study to cast ion outflow observations in auroral zone boundary coordinates. She gave an overview of a poster describing how the boundaries are identified. She also presented results from the first 300 orbits analyzed. Specifically she showed the occurrence of ion beams and conics as a function of magnetic local time and auroral zone coordinates. The auroral zone coordinates went from 0 at the equatorward boundary to 1 at the polar boundary. The results presented were confusing, as the cusp region did not show the usual signature of intense conic activity. Several modelers present at the session encouraged Dr. Andersson to continue working on this project. Dr. Gang Lu ­ Presented an overview of EISCAT observations of isolated and intense outflow events. Some of these events were associated with electron precipitation and some not. The events seem to be correlated with the region of convection reversal. Dr. Chris Mouikis ­ Presented mass resolved, energetic ion composition observations from the Cluster/CIS instruments in midnight tail region near 19 Re. He is aiming to resolve the effect of O+ on tail dynamics and storms. The data he presented for 17 Aug 01 - 10-17 UT, showed double beams showing bouncing ion streams, with energies dispersed. He also reported Energetic O+ tailward of the reconnection site in this event. The data appear very good. We are looking forward to seeing a quantitative analyses of the data at future meetings. Dr. Simon Wing ­ Presented analysis of dayside cusp ion distributions observed on the DMSP satellite in the framework of a model he and his colleagues have developed. The model predicts the magnitude of an electric field at the magnetopause. Dr. Pontus Brandt ­ Presented results from the low energy neutral mass spectrometer that flew on the Swedish Astrid satellite. He showed low energy (~100 eV) Oxygen neutrals originating on field lines well inside the polar cap. These data were obtained before the IMAGE/LENA observations and are in the process of being compared with them. Ms. Karen Remick ­ Presented Incoherent Scatter Radar (ISR) observations she interprets as the signature of ion outflows. She showed that most of the ISR data points were not associated with ion outflow. She concluded that heating by electrons in the topside ionosphere is associated with many ion outflows. It was not clear how these observations extend the statistical analysis of ion outflows in the less than 1000 km region obtained from DE ­2 by Loranc, Heelis, and their coworkers. Dr. Tom Moore - Auroral and Lobal Winds One chart showing the types of distributions seen over the poles, in the lobes, and into the plasma sheet during Fall 2001 Polar equatorial period. Hot auroral flows are embedded within pervasive cold lobal winds. Neutral sheet is either bidirectional streaming for thick NS, or isotropic hot for thin NS. The identification of bistreaming with the PSBL as being of ionospheric bihemispheric origin was somewhat controversial. Session on Polar Wind Contribution to Magnetospheric Plasmas Dr. Peterson¹s introduction on the polar wind and the difficulty of obtaining synoptic measurements of its properties precipitated a discussion about how the polar wind can be distinguished between ion outflows on auroral field lines. The general consensus was that the polar wind is a seed population that can and is energized by many other processes. Dr. Takume Abe ­ Presented detailed movies of primarily polar wind velocity obtained from more than a solar cycle of observations from the Canadian SMS instrument on the Japanese Akebono (EXOS-D) satellite. He showed that the velocity of the polar wind decreases with increasing solar activity. Polar wind velocity increases with magnetic activity (Kp >3). His movies of the data sorted into geomagnetic coordinates as a function of solar and geomagnetic activity show that the region of outflow expands significantly with increasing solar and geomagnetic activity. Many of the variations of polar wind plasma properties presented were counterintuitive which initiated a lively discussion. It is hoped that Dr. Abe and the SMS analysis team will make these results available in a useful form for the modeling community. Dr. Pat Newell ­ Noted that there should be a direct relation between polar rain and polar wind. He suggested that the presence of polar rain electrons should modify the ambipolar field accelerating the polar wind. Evidence supporting this was cited by Tom Moore, from Polar experience. Dr. Mark Hairston ­ Presented analysis of DMSP ion drift data obtained during an over flight of an EISCAT radar during an active period. He had been asked by Drs. Gang Lu and Bill Peterson if the ion drift observations were capable of identifying thermal molecular ion outflow (i.e. N2+, O2+ or NO+) He discussed the limitations of the DMSP instrument package ---temporal resolution, energy range, and assumption of a thermal plasma. He noted that the next generation of DMSP ion drift instruments will have significantly higher temporal resolution than the current 4-s. The bottom line was that the event of interest probably did contain significant upwelling thermal molecular ions, but the temporal resolution of the instrument precluded resolution of the most interesting part of the data. Dr. Bill Peterson ­ Presented a re-sorting of published energetic ion outflows flows above 15 eV from three years of Polar perigee passes. The data were binned by solar zenith angle (SZA), Kp, INVL, and MLT. Complete coverage was limited to the dawn/dusk region because complete SZA coverage is not available for the cusp and midnight regions of the auroral oval. He showed that, during geomagnetically quiet times, the flux of energetic H+ and He+ decreases with increasing solar illumination. He suggested that charge exchange with thermal O+ component of the polar wind in sunlight is the cause of this unexpected variation. Dr. Tom Moore presented arguments that the polar wind should be regarded as a continuous outflow that is unresponsive (in flux) to magnetospheric inputs, though it does respond in velocity as shown by Dr. Abe. He asserted that the polar wind flux should be regarded as a given for all global simulations, and that they should endeavor to form a plasmasphere by trapping this flux on low latitude flux tubes. Changing magnetospheric convection would then make that outflow available at higher latitudes. Dr. Jim McFadden ­ Reported observations of cold ion streams in the plasma sheet at 19 Re observed by the Cluster CIS plasma instrument package. The suggested that this was the observation of energized polar wind in the tail. He also noted that cold ions are also often seen above the Cluster spacecraft potential near the magnetopause, apparently reflecting either plasmaspheric or polar outflows. Joint WG1/2 session on Ionospheric Outflow Response to Imposed Auroral Energy Inputs. Dr. Jay Johnson ­ Presented detailed analysis of a FAST He+ ion outflow event. He used the observed wave spectrum (in the BBF frequency range) on FAST, propagated it to lower altitudes and showed that the observed flux of energized upflowing He+ was consistent with its being energized below FAST by the broad band wave spectrum observed at FAST, assuming it was prorogating downward. The subsequent discussion compared and contrasted his analysis with previous, reports and supports the conclusion that a significant fraction of heavy ions are energized by broadband waves in the altitude region below a few 1000 km. Dr. Yi-Jiun Su ­ Presented an overview of her recent work on identifying ion and electron acceleration events in the so-called ³Alfvenic² region of the auroral oval. The FAST team has determined that there are three different types of auroral acceleration regions sorted in latitude. The upward and downward current regions and the ³Alfvenic² region. This region is characterized by intense, low frequency, fluctuating electric fields. Dr. Su showed t hat separation of the ³Alvenic² region is not always easy. She presented a comparison of ion outflow vs. pointing flux from various regions and illustrated a strong correlation between them in the ³Alfvenic² region. Dr. Steven Mende ­ Expanded on the observations (discussed above) he presented in the WG 1 Session on Auroral Outflow Contributions to Magnetospheric Plasma. In particular he noted that the intense optical emissions assoicated with proton precipitation at substorm onset move systematically dawnward, contrary to expectation. Dr. Bill Lotko ­ outlined the basic basic theoretical concepts involved in auroral acceleration of ionospheric ions (FAC system, auroral density cavity, Knight relation, Bohm Criterion) and discussed their relationship to the problem of the ionospheric response. He noted that a treatment of field aligned potential drops is an essential part of simulating the overall MI-interaction, since these regulate outflow energy or velocity, thereby influencing convection paths. There was some discussion about whether E// should be covered by the ionospheric boundary condition or within a global simulation. Joint WG1/2 session on implementing a MI Coupling Challenge The spirited discussion during this well-attended session revealed considerable interest among observers, modelers and theoreticians in three general problem areas: 1) distributions of energy and energy flux of electron precipitation (more generally electron parallel energization); 2) distributions of the mass flux and composition of outflowing ions, the processes determining them, and the impacts of ionospheric mass outflow on magnetospheric processes; and 3) distribution and length-scale dependence of ionospheric Joule heating. Global, regional and local distributions in space and time are of interest. The discussion also revealed different expectations in the outcome of a MI coupling challenge. Global models require large data sets for code validation and the formulation of reduced models and/or parameterizations of the fluxes and transport that define MI coupling and boundary conditions in terms of MHD or macro variables, e.g., mass outflow rate in response to ionospheric energy deposition rates, if simple relations of this type exist. Modelers therefore expressed a need for relatively simple physical reductions from theoreticians and empirical relations from observers in order to implement appropriate ionospheric outflow boundary conditions and to improve existing electron precipitation models, together with appropriate data needed to validate the performance of such relations in large-scale codes. Alternatively, the interpretation of data is facilitated by results from theory and models that quantitatively address the impacts of mass exchange and energy deposition on magnetospheric circulation, including feedback loops. Observers therefore want quantitative theoretical and model results that can be tested against data and that will serve to organize and interpret the data and facilitate understanding of causal relations. Given the current state-of-the-science, we seem to be confronting a chicken and egg problem. It also appears that a productive MI coupling challenge will likely require a joint effort of CEDAR and GEM. In view of the different expectations, needs and scope of a MI coupling challenge, the working group co-chairs and campaign coordinators propose to use event studies to encourage the development of the tools needed to make further progress, in particular, to assess the physical-empirical outflow relationship to energy input on the ionospheric end, and the modeling methods to accommodate corresponding ionospheric plasma inflow into the global simulation models. The first task will involve the identification of several intervals or events that can be characterized as completely as possible by both observers and modelers given the current state-of-the-science. Special attention should be devoted to the following processes: a) energy transfer from the magnetosphere to the ionosphere, in all forms; b) the state of the topside ionosphere, plasmasphere, and plasma sheet; c) the outflow of ionospheric plasma in response to the inputs; d) system behavior as modeled with/without the ionospheric mass transfer. This discussion will be continued at the GEM Fall AGU mini-workshop where we hope to identify at least two intervals for further study, with the intention of challenging observers to return to the 2003 GEM summer workshop prepared to characterize the ionosphere and its contribution to the magnetosphere. The best ion mass spectrometer data from FAST, Polar, and Akebono are available in 1997, suggesting that one of the intervals should be in 1997. The recent launch of TIMED and availability of data from IMAGE and Cluster suggests that one of the intervals should be after February, 2002. +-------------------------------------------------------------------------+ |To add name to the mailing list or for a message to the GEM community | | please contact: editor at igpp.ucla.edu | | | |URL of GEM Home Page: http://www-ssc.igpp.ucla.edu/gem/Welcome.html | |Please update your e-mail address. | +-------------------------------------------------------------------------+