Enhanced Ionospheric Outflow During SEP Events

Motivation:

1. Jackman et al., GRL, 2883-2886, 2001. Northern hemisphere atmospheric effects due to the July 2000 solar proton event.

   Background NOx levels are typically 1-5 ppbv @ 0.3 hPa and 20-60 ppbv @ 0.01 hPa. During the July 2000 SEP event HALOE observed NOx levels (50-80km altitude) at 50 ppbv @ 0.3 hPa and 200 ppbv @ 0.02 hPa.

   Note that for the July, 2000 event, SEPs impacted the Polar spacecraft at ~1100UT on July 14. Min in DST index occurs ~0000UT on July 16. IP shock detected at Ace at ~1415UT on July 15.
   

2. To what extent does an increased supply of these neutral products at middle atmosphere altitudes provide an increased outflow of ionospheric heavy ions to the magnetosphere?

   Recall the work of Cannata and Gombosi [1989]: Increased thermosphere heating (by as much as 60%) occurring as a result of the transition from solar minimum to solar maximum increases the scale height of light and heavy neutrals, and thus the potential supply of light and heavy ions at the topside ionosphere through charge exchange interactions maintaining the O+/H+ ratio in roughly the same proportions as the neutral O/H particle ratio. The increased scale height changes lead to enhanced ionosphere fluxes preferentially for heavier, more gravitationally bound species.
   

TIDE Observations:

1. There is a difficulty of course, consider the July, 2000 event during which the SEPs (2.4x10^4 at GOES) saturate the TIDE detectors until well after the SSC at 1437UT on July 15:

   
   

2. There are other events, with somewhat lower SEP fluxes, that do not completely saturate the TIDE detectors.

   November,2001: SEPs encounter Polar at ~0130UT on Nov 23, SSC at 0556UT on Nov 24. Minimum in DST (-213nT) reached at ~1700UT on July 24.

   First, scan the summary plots:

   
   

   Now, look in more detail at the outflows:

   
   

   Preliminary look at the fluxes at perigee:

   
    

   November,2001: SEPs encounter Polar at ~1730UT on Nov 4, SSC at 0152UT on Nov 6. Minimum in DST (-277nT) at ~0600UT on Nov 6.

   First, scan the summary plots:

   
   

   Now, look in more detail at the outflows:

   
   

   Again, a prelim look at the fluxes at perigee:

   

Information Last Reviewed/Updated: 04 Sept 2002 Responsible NASA Official: Barbara Giles NASA Goddard Space Flight Center, Code 692 Greenbelt, MD 20771