2008 Workshop:Geospace Response to Solar Minimum Drivers
From CedarWiki
Geospace Response to Solar Minimum Drivers - All Solar Minima Are Not the Same
Contents |
Location
Matterhorn
Date/Time
1300-1500 Tuesday 17 June and 1300-1500 Wednesday 18 June 2008
Conveners
- Janet Kozyra
- Larry Paxton
Format of the Workshop
scheduled short-presentations and discussion
Duration
4 hours
Estimated attendance
30
Conflicts with other workshops
none
Special technology requests
none
Forum
Comments, Questions, Discussion Forum
Brief Initial Description
The present solar minimum is unusually deep with monthly sunspot numbers dipping to values below those of the last 4 solar cycles and monthly magnetic activity at levels comparable to the quietest intervals over this same time period. During this time, it was expected that signatures of geomagnetic activity in the upper atmosphere would be at a minimum allowing a clearer view of the coupling with the lower atmospheric regions and raising the possibility of observing the ground-state of the Sun-Earth system. In fact this was the primary geospace science focus for the IHY Whole Heliosphere Interval (WHI) campaign that took place during 20 March - 16 April 2008, cosponsored by the Climate and Weather of the Sun-Earth System (CAWSES) program.
However, first results of WHI raise interesting questions about the standard picture of solar minimum drivers. In this standard picture, during the declining phase of the solar cycle, long-lived high-speed solar wind streams emanating from trans-equatorial coronal holes drive periodic auroral activity at Earth lasting up to 7 days or more and recurring over multiple solar rotations. Moving into solar minimum, these organized fast streams give way to slower solar wind in the ecliptic plane and magnetic activity at Earth decreases as coronal holes retreat to the polar regions on the Sun.
During WHI in 2008 observations showed that the nature and distribution of coronal holes near solar minimum had important differences from this simple picture - isolated, trans-equatorial coronal holes persisted throughout the solar minimum interval. The high speed solar wind that arrived at Earth originated from deep within the coronal holes and thus was exceptionally fast and long-lived. In contrast, in 1996 during Whole Sun Month (10 Aug - 08 Sept 1996) and the surrounding solar minimum interval, the Earth experienced wind from the equatorward extension of a polar coronal hole called the ¿Elephant¿s Trunk". The resulting high speed streams, coming mostly from the edges of the narrow coronal hole extension, were weak and disorganized. Since the speed and duration of coronal hole winds have been shown to control the nature and severity of resulting geospace and atmospheric disturbances, the geospace response to solar minimum conditions must vary considerably between solar cycles 22 and 23. All solar minima are not the same.
The purpose of this workshop is to:
(1) Take a first look at the upper atmosphere and geospace response to the persistent high speed solar wind driving during the current solar minimum interval with focus on the WHI 2008 campaign interval;
(2) Compare to conditions during the last solar minimum in 1996 (where possible) with focus on the 1996 WSM interval;
(3) Identify interesting Sun-to-Earth science questions from the ITM perspective as well as focus areas within the ITM system for continuing collaborations with the WHI campaign.
Any and all contributions on these and related topics are welcome. Please contact the conveners.
Presentation Resources
Upload presentation and link to it here. Links to other resources.
