Details

Autor(en) / Beteiligte

• Mohanty, P K
• Arunbabu, K P
• Aziz, T
• Dugad, S R
• Gupta, S K
• Hariharan, B
• Jagadeesan, P
• Jain, A
• Morris, S D
• Rao, B S
• Hayashi, Y
• Kawakami, S
• Oshima, A
• Shibata, S
• Raha, S
• Subramanian, P
• Kojima, H

Titel

Transient Weakening of Earth's Magnetic Shield Probed by a Cosmic Ray Burst

Ist Teil von

• Physical review letters, 2016-10, Vol.117 (17), p.171101-171101, Article 171101

Ort / Verlag

United States

Erscheinungsjahr

2016

Quelle

American Physical Society Journals

Beschreibungen/Notizen

• The GRAPES-3 tracking muon telescope in Ooty, India measures muon intensity at high cutoff rigidities (15-24 GV) along nine independent directions covering 2.3 sr. The arrival of a coronal mass ejection on 22 June 2015 18:40 UT had triggered a severe G4-class geomagnetic storm (storm). Starting 19:00 UT, the GRAPES-3 muon telescope recorded a 2 h high-energy (∼20  GeV) burst of galactic cosmic rays (GCRs) that was strongly correlated with a 40 nT surge in the interplanetary magnetic field (IMF). Simulations have shown that a large (17×) compression of the IMF to 680 nT, followed by reconnection with the geomagnetic field (GMF) leading to lower cutoff rigidities could generate this burst. Here, 680 nT represents a short-term change in GMF around Earth, averaged over 7 times its volume. The GCRs, due to lowering of cutoff rigidities, were deflected from Earth's day side by ∼210° in longitude, offering a natural explanation of its night-time detection by the GRAPES-3. The simultaneous occurrence of the burst in all nine directions suggests its origin close to Earth. It also indicates a transient weakening of Earth's magnetic shield, and may hold clues for a better understanding of future superstorms that could cripple modern technological infrastructure on Earth, and endanger the lives of the astronauts in space.