*************************** ** THE GEM MESSENGER ** *************************** Volume 7, Number 27 July 8, 1997 -------------------------------------------------- 1997 SNOWMASS REPORT: TAIL/SUBSTORM CAMPAIGN WG 1: -------------------------------------------------- From: Larry Lyons ************************************************************* Our working group proposed the following more focused goal: Develop a phenomenological picture of substorms in time and space. This picture should be: 1. Observationally based, and not biased by particular substorm models 2. Eventually turned over to the GGCM community as a challenge for testing models. 3. Used to open doors for people (include those new to the substorm community) to add new information into the picture The above goal of developing a phenomenological picture of substorms was adopted by the steering committee, and new working group chairmen are being selected. We anticipate that some of our working groups studies will be useful for the phenomenological model development and that some of the events may be appropriate for "challenges" of the modeling community. We thank all those that have participated in our working group for their efforts during the past few years, and we encourage the completion of studies that have been initiated. ************************************************************* WE HAD THREE 2-hr SESSIONS AS FOLLOWS: A. MONDAY 16 JUNE 10-12: Ad-hoc GEM intervals LUI: results from classic isolated substorm at 0430 UT on 9 Feb. 1995 with comprehensive ISTP observations. Apparently triggered by the IMF. Total pressure decreases at GEOTAIL (x ~ - 30 RE) at onset. No evidence for neutral line in association with onset. WINGLEE: Modeled Lui event. Reproduced large-scale GEOTAIL B, but not substorm effects on B. RODGER: Nice isolated substorm on March 9, 1995, at 0248 UT with excellent ISTP data and a 1 hr and 20 min growth phase. (NO DISCUSSION since Alan Rodger could not attend) SANCHEZ: Analyzed data from onsets at ~2230,~2250, and ~2310 UT on Feb. 7, 1996. Found pulsations with 1.5 mHz response at three widely spaced location (ground, geosynchronous orbit, and GEOTAIL at x ~ - 25 RE) in association with onset R. NAKAMURA: GEOTAIL (x ~ - 25 RE) tail response to the IMF and to isolated substorm onsets on Nov. 22, 1995. Found total pressur up in tail when solar wind E went up prior to substorms, and total P down after onset. The total P also went up for one event when the IMF Bz stayed positive and for which there was no substorm. REEVES: Evaluated substorm onset timing using very conjugate ground and geosynchronous observations. Found that it is essentially impossible to discern onsets to < 3 min, and in particular that two ground stations ~2 degrees in longitude apart saw 3 min different Pi 2 and ground delta-H onsets. LYONS: a. Compiled set of 20-30 onsets with GEOTAIL-CANOPUS conjunctions. Initial examination suggests that total pressure in tail (x = -13 to -31 RE) goes down in association with all but one of the onsets. To be analyzed in more detail in collaboration with T. Nagai. b. Compiled set of onsets of classical substorms in N. America sector (20) and in Scandinavian sector (9). To be used to evaluate ground convection and geosynchronous pressure response to substorms in collaboration with. A. Steen, R. Greenwald, K. Baker, and G. Reeves. SANCHEZ Discussed data from 0000 to 0400 UT on the Sept. 10, 1996 with onset at 0207 UT. Has Sondrestrom flows and POLAR images, so can relate flows to conductivities. B. MONDAY 16 JUNE 3:30-5:30 p.m.: GEM intervals during WIND perigee passes. SLAVIN (MAYNARD): Three satellites in tail for three major onsets on April 18, 1996. See responses over wide range in y, which implies that a large y-extent of the tail is involved in onset. SANCHEZ: Initiating study of 2215 UT onset on Sept. 16. 1995. WIND saw dipolarization at ~2245 UT. ELSEN: Showed data from a well observed (UVI, AKR, ground, geosynch.) onset at 0400 UT on May 10, 1996. WIND dipolarization observed also. BAKER: Found that flows observed by SuperDARN decreased throughout night-side during 8-10 min interval following 040 UT onset on May 10, 1996. ANGELOPOLOUS (TEMERIN): Did BBF study when GEOTAIL and WIND 3 RE apart from 9-14 UT on March 27, 1996. Found that not all BBF's are associated with magnetic bays, but found a UV emission response to all detected BBF's. MCPHERRON: Studied 0353 UT onset on Nov. 28, 1995. Found that GEOTAIL at x = -30 RE saw tailward flow for 15 min prior to onset. At the same time B was almost entirely in the y direction. C. TUESDAY 17 JUNE 10-11:00 am: New ISTP events January 1,2, 1997 FOX overview: GEOTAIL and IMP cross midnight together at ~30 and ~ 38 RE. Very small onsets at ~2145, 2200 on the 1st. A well defined but moderately small onset at 0157 on the 2nd. LUI: No evidence for neutral line signatures ( Bz < 0 or tailward flows) at x ~ 30 RE and y ~ 0 prior to onsets. Good examples of small events; data to be put on line for all (http://www-spof.gsfc.nasa.gov/istp/events/gem/) D. April 7-11, 1997 (http://www-spof.gsfc.nasa.gov/istp/event_apr97/index.html) FOSTER: Overview of available good ground coverage LYONS: Good period for studying IMF-substorm relations for non-ideal events, because of good ground and IMF coverage, (April 10-11) _____________________________ Nelson Maynard (nmaynard at mrcnh.com) Larry Lyons (Larry at atmos.ucla.edu) +-------------------------------------------------------------------------+ |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 | | | |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! | +-------------------------------------------------------------------------+