*************************** ** THE GEM MESSENGER ** *************************** Volume 5, Number 22 September 25, 1995 --------------------------------------------------------- Report on GEM Snowmass Meeting, June 26-30, 1995 - Part V --------------------------------------------------------- TAIL/SUBSTORM CAMPAIGN WG 1: SUBSTORM SIGNATURES; IDENTIFICATION, LOCATION, AND TIMING Co-Chairs: Nelson Maynard and Larry Lyons WG-1 is data oriented with a focus of defining an accurate spatial and temporal description of the substorm process in the magnetosphere and ionosphere. The timing of events in one region relative to another is critical to address the questions of cause and effect. It is our intent to assemble definitive data sets that can address key science issues and with which models of substorm processes can be tested and validated. At Snowmass last year three sets of events were identified for coordinated data collection and study. Data were gathered and sent to the coordinators for the initiation of collaborations. A series of substorms in March 1993 was coordinated by Lyons. The January 11-14, 1994 period which featured GEOTAIL at 90 Re was coordinated by Maynard. Hughes coordinated several events with CRRES data from 1991. Each of the coordinators developed time lines for each event which were presented at the December meeting at San Francisco and again at the Snowmass meeting this year. These are available by request to the appropriate coordinator. A large amount of data have been supplied, some of which are available through Mosaic home pages. We are extremely pleased with the cooperation of all who have sent data. We would like to reiterate, as we proceed to the analysis phase, that the studies need to remain coordinated. Rules of the road should be the same as those on a number of recent satellite programs: _____________________________ If you use someone's data, offer that person a chance to be part of the study, to have the option of participating as a co-author or to add any necessary and pertinent caveats. Keep the data suppliers and coordinators informed as to who is pursuing what topics and events. _____________________________ Analysis continued at Snowmass this year. Each of the three sets of events, were reviewed, including the time lines and representative data for each period. In addition, an ad-hoc interval (not a pre-scheduled GEM period) from 9 March 1995 was added, with Alan Rodger as the coordinator. Particular interest in the previously scheduled 94/95 winter GEM periods has not yet been generated. Brief synopses of where the analyses stand are given below. The March 95 event is another event involving the ISTP satellites emphasizing this rich source for collaborative studies. GEM intervals for the coming year are being picked to correspond to particularly interesting configurations of the ISTP satellites (see recent WG 1 report for the Boundary Layer Campaign). With the sucessful launch of Interball and the upcoming launches of POLAR, FAST, and Cluster, the opportunity for studies of ground-based data in conjunction with satellite data are rapidly expanding. Discussions were held with POLAR and WIND project leaders on how to best work together to maximize the scientific output. Nelson Maynard will be the focal point for interations between GEM and ISTP and Jim Green will serve that role on the ISTP side. Their roles will be to facillitate the direct contacts needed between the communities needed to do the science. The GEM forum provides a unique focal point for interaction between the ground-based and satellite investigators. With this opportunity comes an imperitive. Extended missions for WIND and POLAR will be justified next spring and summer. Good science coming from coordinated studies will be a primary factor in the process. This means that in addition to finishing the studies in progress, we need to focus quickly on GEM periods from this fall and winter. More information will be forthcoming about this fall and winter later in the plans for the December Workshop at San Francisco. A. CRRES Events (Hughes) Five periods had been previously selected as potential candidate events with which to study substorn onset signatures, particularly issues around the relative timing of various signatures observed near synchronous orbit and from the ground around substorm onset. All were chosen as being substorm onsets seen by the CRRES spacecraft at times it was near apogee (6.3 Re) and over the CANOPUS network of ground observatories. The candidate events were: Date CRRES Orbit No. Onset Time (approx) Study Interval 24 Jan 1991 444 0810 0700-0900 9 March 1991 551 0200 0100-0300 9 March 1991 551 0600 0500-0700 23 March 1991 585 0235 0130-0330 2 August 1991 902 0600 0500-0700 At the Snowmass Workshop the timeline for each event and a synopsis of the data collected thus far was presented. The data are primarily field and plasma data from CRRES, GOES magnetometer data and Los Alamos particle data from synchronous orbit, and CANOPUS meridian scanning photometer and magnetometer data. In addition Greenland magnetometer data and SuperDARN HF radar data were available for most events, but geographically removed from the satellite footprints. For each event the question was then asked: Is this data set useful for addressing one of the questions identified as important for the substorm/tail campaign? For two of the events, the consensus was that the CRRES data and the particular conjunction would provide a unique opportunity, for other events the data would provide useful additional information to other studies. 24 Jan 1991, 0802UT: At 0802UT a well defined onset occured in magnetometer and photometer data from Fort Smith and Fort Simpson in the Yellowknife sector and close to the foot of the CRRES field line. Effects at CRRES (magnetic field dipolarization, electron injection), and at the two GOES s/c, located roughly an hour in local time either side of CRRES, occured some 5 or 6 minutes later. Since the ground onset was observed so close to the nominal foot of the CRRES field line, it was felt that this event would provide a good case study for examining delays between ground and synchronous orbit signatures. Thus scientific analysis should proceed. Hughes will lead this study. 9 March 1991, 0602UT: An onset occured at 0602UT when CRRES and GOES 7 were very close, and within uncertainties, in the same meridian plane, very close to the CANOPUS Churchill meridian chain of magnetometers and photometers. An auroral brightening and polarward expansion as well as Pi2's were seen on the ground. Both CRRES and GOES 7 observed dipolarizations and FAC signatures, while CRRES wave and plasma data also had good signatures. Even though this was a weak substorm (almost no AE signature, and only small auroral magnetogram bays) the consensus was that the very close conjunction of two s/c at onset made this event interesting, as it allows study of the spatial and temporal structure of synchronous dipolarizations. Hughes and Singer will lead this study. 23 March 1991, 0215UT; At 0215UT an onset occured in the Halley/Greenland sector. CRRES, some distance to the west, began to see effects at 0224UT, while the main dipolarization and electron injection occured at 0235UT. The Halley radar was in a good position to see flows associated with this onset. Pinnock and Rodger will lead a study of this event focusing on the radar signatures. 2 August 1991, 0600UT: CRRES was near the dusk terminator when this onset occured, and no field data are available. B. Jan. 11 - 14, 1994 Events (Maynard) This interval is particularly rich in activity, and GEOTAIL was at 90 Re in the tail. Studies of the relationship of events in the tail relative to substorm onset are possible. The most frustrating aspect of the interval is the spottiness of the IMF data. A number of substorms have been identified. In general the response at GEOTAIL is happening after ground onset. Throughout this period GEOTAIL experiences many intervals of sunward flow indicating the the X-line is tailward of the satellite. In other periods the satellite is in the lobes or in tailward flowing plasma sheet fluxes. On January 12 the substorm onset was identified at 04:30 at geosynchronous. First ground identification at 04:49. May be multiple intensifications. Tailward moving structure seen at 04:50 to 05:18 at GEOTAIL (satellite in lobes before and after). On January 13 the substorm onset was at 00:47.5 at Greenland. GEOTAIL entered plasmasheet from lobe with gradually increasing tailward flow. Satellite later reenters lobe and returns. Later substorm at 03:14 (onset at Gillam). Tailward flow seen after 03:22. Events on these two days may represent cases of plasmoids or flux ropes or changes in the plasmasheet boundary layer. Investigation is continuing. Nakamura and Angelopoulos have agreed to take the leadon these events. On January 14 a substorm was detected at Gillam at 06:29. At 06:37 the flow direction shifted from earthward to tailward at GEOTAIL Several substorms also occurred near the end of the day as the satellite mapped to the scandanavian sector. At GEOTAIL the flow reversed a number of times between earthward and tailward. This period has a very variable IMF. Initial interpretation is that the X-line moved several times inside and then outside of the satellite. Good ground coverage from Svalbard in the later period will allow the high latitude aurora to be correlated with the events at GEOTAIL. Maynard is taking the lead on this study. An abstract has been submitted to AGU. These events represent the first GEM events involving coordination with an ISTP satellite. Other periods within this interval may also be of interest and may be pursued later. We expect future GEM campaigns to feature ISTP collaborations and hope they all work as smoothly as this one. C. March 17-25, 1993 Events (Lyons) A variety of substorm events have been identified that have good ground magnetometer, radar, optical, and geosynchronous satellite data. GEOTAIL data are available from near 200 RE. At Snowmass this year it was decided to focus on the following events and studies: 24 MARCH 0233 (and 0450 UT) ONSET: Good data coverage at onset with good radar flow data (at least during 0233 substorm) 1. Obtain and evaluate best possible radar flows relative to 0233 onset [Pinnock, Lyons, Ruohoniemi] (in progress) 2. Detailed evaluation of precipitation relative to 0233 flows [Rosenberg] (to be started) 3. Correlative study of IMP 8 in tail and GEOTAIL much further out in tail for both onsets [Mitchell, Angelopolous] (nearly complete) 4. Reconnection rate at Sondrestrom relative to 0450 onset [Blanchard, Lyons] (in progress) 5. Evaluate flows relative to 0450 onset [Pinnock] (to be looked at) 20 MARCH 0452 ONSET (GEOTAIL in sheath) Excellent onset timing event, with 2-point boundary measurements and possibly good radar flow data 1. Potential for a good study; first need to examine quality of Goose and Halley data [Pinnock, Rodger, Lyons] (to be looked at) 21 MARCH 0355, 0530 ONSETS: Good onset identifications 1. Radar flows to be evaluated for quality [Pinnock] 2. Possible GEOTAIL interest [Nakamura, Angelopolous] 18 MARCH 0012 UT ONSET: Well defined onset, but not good flow data from Halley and Goose Bay radars. 1. Possible GEOTAIL interest [Nakamura, Angelopolous] The flowing events have been identified but not selected for study: 17 MARCH 2350 ONSET: Does not appear to be a typical substorm? Has some characteristics of polar-cap boundary events 20 MARCH 0234 ONSET: Small event with little radar echoes 20 MARCH 0400 ONSET: Small, localized but well-defined substorm that temporally interrupts growth phase; few Halley or Goose Bay echoes 20 MARCH 0530 ONSET: Period could be useful for detailed Goose-Halley study of flow changes within plasmasheet and in vicinity of polar-cap boundary 25 MARCH 0519 ONSET: Good classic substorm event for study if can get good Goose, Halley flows; Goose echoes limited, Halley data not looked at in detail 25 MARCH 0557 ONSET: Onset west of CANOPUS, few Halley or Goose echoes D. Ad hoc interval: 9 March 1995 Event (Rodger) The Wind spacecraft, about 200 Re upstream in the solar wind near the sun-earth line, detected a rapid southward turning of the interplanetary magnetic field at 0248 UT on 9 March 1995, after an extended interval (>24 hours) when the field had been northward. Therefore the magnetosphere was close to a quiescent state. One hour after the southward turning, a relatively simple and extended growth phase started that terminated with substorm onset near 0500 UT. At this time, Geotail and IMP-8 were located in the nightside magnetosphere near the equatorial plane at -13 and -30 Re respectively, and therefore were ideally placed for making critical measurements in each of the three accepted phases of the substorm. The activity was centred over North America and the North Atlantic in the northern hemisphere, and the Weddell Sea Sector of Antarctica in the south: areas that are very well instrumented with magnetometers, all-sky imagers, riometers, and the SuperDARN radars. These high time resolution space- and ground-based data of outstanding quality when combined with the LANL, GOES and DMSP spacecraft data, are likely to provide a unique view in latitude, longitude and altitude of this comparatively simple substorm. The results from this study should be of considerable value in the identification of the successful features and the limitations of the various competing substorms models. Alan Rodger (British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, UK, e-mail A.Rodger at BAS.AC.UK, fax 44-1223-362616) has agreed to act as coordinator for this interval. All those with relevant data sets are asked to send copies of their data for the interval 00-06 UT either electronically ofr by fax before 15 October 1995. Co-Chairs: Nelson Maynard (maynard at zircon.plh.af.mil) Larry Lyons (larry_lyons at qmail2.aero.org) Nelson Maynard +-------------------------------------------------------------------------+ |To add name to the mailing list, send a message to: editor at igpp.ucla.edu | |For message to whole GEM mailing list, send to: gem at igpp.ucla.edu | |For message to a specific working group (BL Campaign), send to: | | gem_field at igpp.ucla.edu (WG1); gem_boundary at igpp.ucla.edu (WG2); | | gem_current at igpp.ucla.edu (WG3); gem_data at igpp.ucla.edu (WG4) | | gem_ggcm at igpp.ucla.edu (WG5) | | gem_chair at igpp.ucla.edu (WG chairs, Odile and W. J. Hughes) | | | |URL of GEM Home Page: http://igpp.ucla.edu/gem/Welcome.html | |Please update your e-mail address. | |CAUTION: Do not send messages to gem at igpp.ucla.edu unless you want | | your message to go to everyone in the GEM mailing list! | +-------------------------------------------------------------------------+