The importance of solar wind magnetic field observations & the upcoming Sunjammer solar sail mission J. P. Eastwood The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK 13 November 2013 RMS RAS Joint Meeting: Space Weather: The Importance of Observations Imperial College London
Summary The near Earth space environment and space weather Measuring the Interplanetary Magnetic Field upstream of the Earth Sunjammer MAGIC: Magnetometer from Imperial College Conclusions
The Earth s magnetosphere (Movie credit: NASA)
The solar wind magnetosphere interaction The solar wind is magnetized Eastwood, Phil. Trans. R. Soc. A, 2008 If the solar wind magnetic field is oppositely directed to the Earth s magnetic field, magnetic reconnection allows solar wind plasma, momentum and energy to enter the magnetosphere Energy is stored in the magnetotail, and is explosively released leading to geomagnetic substorms and storms. Strongest driving for fast solar wind with southward magnetic field
Coronal Mass Ejections Movie & Figure courtesy of SOHO /LASCO consortium. SOHO is a project of international cooperation between the European Space Agency (ESA) and NASA. Fast moving CMEs drive bow shock waves Strong, compressed B field in sheath region Smoothly rotating magnetic fields inside CMEs can leads to long intervals of southward IMF Cannot predict CME magnetic field structure from remote observations
Unloading processes substorms and storms Substorms Storms (image credit: NASA) UV auroral emission caused by precipitating electrons (IMAGE; credit NASA) WDC for Geomagnetism, Kyoto
Space weather impacts (Image credit: Bell Laboratories, Lucent Technologies)
Upstream solar wind measurements Have to measure the solar wind magnetic field in situ http://www.nasa.gov/mission_pages/sunearth/news/ace-15th.html
Solar wind phase fronts Figure reference Eastwood et al., Proc. Third International Symposium on Solar Sailing, 2013
Movie & Figure courtesy of STEREO The real solar wind /HI consortium and NASA.
Science questions Existing propagation methods often assume time invariance, and spatial uniformity. However, it is known that: Rapid evolution of the solar wind structure can occur between L1 and the Earth. Even on relatively short spatial scales, there can be significant variation in the solar wind perpendicular to the Sun-Earth line. Solar wind phase fronts are unlikely to be planar on large scales. Different techniques can disagree by up to 30 minutes [Case and Wild 2012] Improved prediction requires a deeper understanding of solar wind evolution, which will ultimately be revealed only by increasing the separation.
Sunjammer
MAGIC: MAGnetometer from Imperial College Novel magnetoresistive design Less than 500mW power 15g sensor head, 150g electronics board P. Brown et al., Meas. Sci. Tech., v.23, 25902, 2012
CINEMA 3U CubeSat form factor 30cm long, 3kg 1m stacer boom Spin-stabilised, 4rpm Magnetotorquers for attitude control S-band communications 1Mbps downlink Two science instruments STEIN, MAGIC Spacecraft designed and built at UC Berkeley, Space Sciences Lab Delivered January 2012 Launch 13 September 2012 Has since suffered from significant communication issues, limiting data return
CINEMA MAGIC magnetometer Implementation of MAGIC on CINEMA Outboard sensor on 90cm boom Science mode <0.25nT resolution, 10 vectors/s Measurements of waves and structures Local magnetic field for particle data Attitude mode Lower power (lower precision, higher noise) Attitude information for spacecraft control
CINEMA magnetic field data Figure reference Eastwood et al., Proc. Third International Symposium on Solar Sailing, 2013 Orbit: 770 km x 480 km, inclination 64º Data is from inboard sensor, in attitude mode and indicates that MAGIC is operating nominally (data transfer and communications have been very limited due to communication difficulties)
MAGIC on Sunjammer Sunjammer is a prototype for the next generation of space weather beacons, but the payload must be lightweight, and any effect of the sail on measurements must be understood. The MAGIC experiment onboard Sunjammer will: test new miniaturised sensor technology beyond LEO for the first time (implementation will change from CINEMA), assess the suitability of solar sail platforms for measuring space plasmas, measure the magnetic field structure of potentially geo-effective Earth-directed events (ICMEs and CIRs), perform scientific investigations of solar wind-magnetosphere coupling. Will potentially increase the warning time of geo-effective solar wind events.
Conclusions Eastwood JP et al., Magnetic field measurements from a solar sail platform with space weather applications, Advances in Solar Sailing, Springer, 2014 Structure in the solar wind magnetic field can cause space weather (e.g. geomagnetic storms) at Earth. The solar wind magnetic field must be measured in situ. To improve warning times, monitoring platforms operating further upstream of the Earth than existing satellites are ultimately needed, but the evolution of the solar wind must be understood. MAGIC, as part of the Sunjammer payload, will: Investigate the feasibility of using solar sail platforms for making magnetic field measurements, Conduct scientific studies of the solar wind magnetic field to better understand the fundamental sources and causes of space weather. Acknowledgements: Sunjammer at ICL is funded by UKSA