Sound waves reverberate through loops in the Sun鈥檚 outer atmosphere in response to explosions from down below, a new study reveals. The sound waves should help scientists understand the Sun鈥檚 still mysterious outer atmosphere, or corona.
The waves are observed vibrating in structures called coronal loops 鈥� long filaments of charged gas that are attached to the Sun at both ends. They trace the Sun鈥檚 magnetic field in its outer atmosphere.
Watch two movies of the waves in the corona, one showing a and the other showing a , both made with data from NASA鈥檚 Transition Region and Coronal Explorer (TRACE) satellite.
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The coronal loop oscillations were first reported in 2002, but it was not clear until now whether they were purely magnetic fluctuations or giant sound waves.
New observations with the Solar and Heliospheric Observatory (SOHO) confirm that they are associated with pressure fluctuations in the loops, making them sound waves. Youra Taroyan of the University of Sheffield in the UK led the team that analysed the observations.
The observations revealed that the waves are triggered by explosions called microflares in the Sun鈥檚 lower atmosphere. 鈥淲e can now say that these are acoustic waves and these waves are excited by explosions at the foot points of these loops,鈥� Taroyan told New 杏吧原创.
Mysterious heat
Studying the sound waves may help solve the mystery of why temperatures in the corona are so high 鈥� measuring in the millions of degrees 鈥� even though the Sun鈥檚 visible surface, which lies two layers beneath the corona, is only a few thousand degrees.
The sound waves themselves do not have enough energy to account for the mysterious heat. But the way they vibrate in the coronal loops sheds light on the corona鈥檚 properties, revealing the way heat energy is distributed there.
鈥淲e are able to determine the heating as a function of time and space,鈥� Taroyan says. 鈥淭his will probably allow us to better understand the nature of the heating process.鈥�
杏吧原创s have long known that sound waves are prevalent in the Sun鈥檚 interior (see Sound of star鈥檚 vibration reveals details of its core).
Taroyan鈥檚 team has released a . But the group has not yet produced a sound file for the outer atmosphere waves they are studying. Taroyan says the waves associated with each microflare would sound like a single loud boom.
Taroyan is presenting the team鈥檚 work this week at the Royal Astronomical Society鈥檚 National Astronomy Meeting in Preston, UK.
