Sun-Earth Connection and Space Weather

1. CSI 769-001/PHYS 590-001 Solar Atmosphere Fall 2004 Lecture 14 Dec. 08, 2004 Sun-Earth Connection and Space Weather

2. Today’s solar wind

3. Solar Wind • Solar wind is a continuous outflow of solar particles, largely due to the thermal expansion of high temperature corona (~ 1MK). • Due to the high thermal conductivity of coronal plasma, the solar atmosphere maintains high temperature even at large heliospheric distance, e.g., ~200,000 K at 1 AU. • Because of this extended temperature distribution, the solar atmosphere maintains a finite thermal pressure even at large distance. • Since the thermal pressure of the solar atmosphere can not be balanced by the external pressure (at large distance), the heliosphere can not be in a hydrostatic equilibrium; it expands.

4. Solar Wind (cont’d) • The typical solar wind speed is about 400 km/s, which is consistent with Parker’s standard solar wind model that is based on hydrodynamic equations (see textbook section 10.1.2 at P.313) According to the model, wind speed of 400 km/s when base temperature of 1 MK

5. Solar Wind (cont’d) • However, observations also show fast solar wind of speed 800 km/s • Fast solar wind is found to be from coronal holes (and CMEs) • Why coronal hole yields fast solar wind is still a mystery! • It is not consistent with Parker’s standard thermal expansion model, because coronal hole has a cooler temperature and therefore a smaller expansion velocity according to the model • There must be non-thermal energy deposition in solar wind in coronal hole regions

6. Solar Wind (cont’d) • Solar wind speed distribution with heliospheric latitude • Slow speed (400 km/s) in low latitude (e.g., < 20 degree) • Fast speed (800 km/s) in high latitude (e.g,, > 20 degree)

7. Interplanetary Magnetic Field (IMF) The basic configuration: Parker Spiral Interplanetary magnetic field in the ecliptic plan

8. Interplanetary Magnetic Field (cont’d) Magnetic Field in the inner corona (< 2 Rs) is mainly closed loops

9. Interplanetary Magnetic Field (cont’d) Magnetic Field in the outer corona (> 2 Rs, but < 10 Rs) is radial

10. Interplanetary Magnetic Field (cont’d) Magnetic Field in the interplanetary space is spiral

11. Interplanetary Magnetic Field (cont’d) • The spiral interplanetary magnetic field is caused by a combination effect of solar rotation and outward transport of magnetic field embedded with the spherical solar wind flow. • Because of high electric conductivity, magnetic field is frozen-in with plasma in the corona and in the heliosphere. Solar magnetic field is carried away by solar wind flow due to frozen-in effect • Solar wind flow is largely spherical along the radial direction • Interplanetary space is a high β regime, the thermal pressure dominates the magnetic pressure; in other words, solar wind flow carries magnetic field with it.

12. Interplanetary Magnetic Field (cont’d) • Well connected magnetic field from the Earth back to the solar surface at about west 57 degree • For a typical solar wind of 400 km/s, it takes 104 hours or 4.3 days to reach the Earth • During the same period, the Sun has rotated 57 degree (using a 27-day rotation period)

13. Interplanetary Magnetic Field (cont’d) • Where is magnetically-well-connected solar region?

14. Interplanetary Magnetic Field (cont’d) • The implications of magnetically-well-connected solar region. • Impulsive SEP events, that are accelerated in flare regions, originate from a narrow region in western hemisphere, because particles move along the spiral field. • When a coronal hole is present in the low latitude, fast solar wind shows in geo-space.

15. Interplanetary Coronal Mass Ejection (ICME) • The counterpart of solar CME in interplanetary space. • They are often caused by halo CMEs that are most likely to intercept the Earth’s orbit. • Solar wind signature of ICME • Shock interface • Enhanced solar wind speed • Enhanced magnetic field • Magnetic cloud • Enhanced plasma density • Reduced proton temperature

16. ICME (cont’d) • Solar wind signature of ICME

17. Space Weather in Geospace • Earth Magnetic Field

18. Space Weather in Geospace • Van Allen Belt: trapped energetic particles

19. Space Weather in Geospace • Magnetosphere

20. Space Weather in Geospace • The impact of ICME on magnetosphere

21. Space Weather in Geospace • A geo-effective ICME usually has a sustained strong southern magnetic field • Southern magnetic field is able to reconnect with the Earth magnetic field that is northern at the interface • Reconnection at the magnetopause allow the reducing of magnetic shield of the Earth’s magnetosphere. As a result, solar wind energy and particles are dumped into the magnetosphere, causing geomagnetic storms

22. Space Weather in Geospace • Ionosphere

23. Space Weather Effects • Solar EM Radiation • Due to solar flares • No warning time • Lasting short (tens of minutes) • Scaled by NOAA GOES Soft X-ray magnitude • Affect Ionosphere • Solar Particle Radiation • Due to flares and CMEs • Short warning time (< 1 hr) • Lasting long (hours to a few days) • Scaled by particle monitor • Direct impact with electronic and human objects • Geomagnetic Storm • Due to CMEs • Possibly a few days warning time • Lasting long (days) • Scaled by Kp and Dst index • Effect throughout the geo-space from ground to the entire magnetosphere

24. Space Weather Effects: NOAA Scale • Five level scaling • Level 5: Extreme • Level 4: Severe • Level 3: Strong • Level 2: Moderate • Level 1: Minor • Solar EM Radiation: R1—R5 (Radio Blackouts) • Solar Particle Radiation: S1—S5 (Solar Radiation Storm) • Geomagnetic Storm: G1—G5 (Geomagnetic Storms)

25. Space Weather Effects: NOAA Scale • Five level scaling • Level 5: Extreme • Level 4: Severe • Level 3: Strong • Level 2: Moderate • Level 1: Minor • Solar EM Radiation: R1—R5 (Radio Blackouts) • Solar Particle Radiation: S1—S5 (Solar Radiation Storm) • Geomagnetic Storm: G1—G5 (Geomagnetic Storms)

26. Space Weather Effects: NOAA Scale • Solar EM Radiation: R5 • HF Radio:Complete HF (high frequency**) radio blackout on the entire sunlit side of the Earth lasting for a number of hours. This results in no HF radio contact with mariners and en route aviators in this sector. • Navigation: Low-frequency navigation signals used by maritime and general aviation systems experience outages on the sunlit side of the Earth for many hours, causing loss in positioning. Increased satellite navigation errors in positioning for several hours on the sunlit side of Earth, which may spread into the night side.

27. Space Weather Effects: NOAA Scale • Solar Particle Radiation: S5 • Biological: unavoidable high radiation hazard to astronauts on EVA (extra-vehicular activity); high radiation exposure to passengers and crew in commercial jets at high latitudes (approximately 100 chest x-rays) is possible. • Satellite operations: satellites may be rendered useless, memory impacts can cause loss of control, may cause serious noise in image data, star-trackers may be unable to locate sources; permanent damage to solar panels possible. • Other systems: complete blackout of HF (high frequency) communications possible through the polar regions, and position errors make navigation operations extremely difficult

28. Space Weather Effects: NOAA Scale • Geomagnetic Storms: G5 • Power systems: : widespread voltage control problems and protective system problems can occur, some grid systems may experience complete collapse or blackouts. Transformers may experience damage. • Spacecraft operations: may experience extensive surface charging, problems with orientation, uplink/downlink and tracking satellites. • Other systems: pipeline currents can reach hundreds of amps, HF (high frequency) radio propagation may be impossible in many areas for one to two days, satellite navigation may be degraded for days, low-frequency radio navigation can be out for hours, and aurora has been seen as low as Florida and southern Texas (typically 40° geomagnetic lat.)**.

29. Space Missions for Space Weather Solar Terrestrial Missions Developmental Operational Under Study Voyager I & II 77 Sich-1 04 RAVENS 07 Ulysses 90 CINDI/CNOFS 04 INTERBALL-PROGNOZ 06-07 SAMPEX 92 TWINS 04,05 STORMS 07 Geotail 92 COSMIC 05 Interhelioprobe 07-08 WIND 94 STEREO 05 L5 Mission 08 SOHO 95 SST 05 Geostorm 09 Polar 96 AIM 06 Auroral Quartet ? FAST 96 THEMIS 06 RESONANCE ? ACE 97 EPOP 06 ROY/SCHWARM? TRACE 98 CORONAS-PHOTON 06 SWISE 10-12 ACRIMSAT 99 SENTINELS 12-14 Solar-B 06 IMAGE 00 Picard 06-07 Cluster 00 Solar Probe 12-14 SDO 07 CORONAS-F 01 GENESIS 01 Iono-Thermosphere Storm Probes 10 TIMED 01 Solar Orbiter 11 RHESSI 02 MMS 12 SORCE 03 Radiation Belt Storm Probes 12 Double Star 03/04 Geospace Heliospheric Solar GEC >12 MC/DRACO >12

30. STEREO Mission

31. (Trajectories) Data Environment http://spdf.gsfc.nasa.gov/ CDAWLib HelioWeb Science Data Facility Science User Sup Acquisition & Ingest Tools & Services

32. Summary • Introduction • Principles of Spectroscopy, Radiation Transfer • Solar Missions and Instrumentation • Solar Magnetic Field, Solar Cycle, and Solar Dynamo • Lower Solar Atmosphere: Photosphere and Chromosphere • Transition Region and Coronal Loop Dynamics • (Midterm) • Coronal Structure • Coronal Plasma Properties, MHD Equations • Ideal MHD, MHD Waves and Coronal Heating • Solar Flare • Solar Flare • Filament Eruption and Coronal Mass Ejection • Coronal Mass Ejection and Solar Energetic Particle (SEP) • Sun-Earth Connection and Space Weather