. Long-term monitoring of energetic protons at the bottom of Earth’s radiation belt
. Long-term monitoring of energetic protons at the bottom of Earth’s radiation belt
复制标题
长期监测地球辐射带底部的高能质子。
作者：
Yoshioka;K.;Miyoshi;Y.;Kurita;S.;Teramoto;M.;Tsuchiya;F.;Yamazaki;A.;Murakami;G.;Kimura;T.;Kita;H.;Yoshikawa;I.;and Kasaba;Y.
众所周知，地球辐射带中的高能粒子在不同的时间尺度上波动。虽然利用卫星进行观测已有50多年的历史，但在位于内辐射带底部的低海拔(2,000平方公里)和低L值(L)地区进行连续和长期观测的例子很少。这是因为被设计为覆盖大片磁层的卫星轨道不适合在低海拔进行长期连续观测。在这项研究中，我们重点研究了通常沿着低空圆形轨道运行的太空望远镜的数据。2013年发射的久崎太空望远镜，从∼1,000公里的高度连续观测行星(L-值1-2)。通过使用Hisaki光电探测器上计数的噪声分量作为辐射监测器，可以观察到该轨道上高能质子(能量为30 MeV)的通量变化。结果表明，太阳活动明显依赖于太阳活动。在L=2附近，发现辐射带质子通量的变化既受星系宇宙线通量的控制，又受热层中性密度的控制。前者是内辐射带高能带电粒子的源过程，后者是库仑碰撞造成的损失过程。研究还发现，银河系宇宙线涨落的影响随着l值向1靠拢而变得更小。
The energetic particles in the Earth's radiation belt are known to fluctuate over various timescales. Although observations using satellites have been made for more than 50 years, there are few examples of continuous and long‐term observations at low altitude (<2,000 km) and in lowL‐value (L< 2) regions, which are at the bottom of the inner radiation belt. This is because the orbits of satellites that are designed to cover large areas of the magnetosphere are not suitable for long‐term continuous observations at low altitudes. In this study, we focused on data from a space telescope that usually follows a low‐altitude circular orbit. The Hisaki space telescope, launched in 2013, continuously observes the planets from an altitude of ∼1,000 km (L‐value 1–2). By using the noise component counted on the photodetector of Hisaki as a radiation monitor, the flux variation of the high‐energy protons (energy > 30 MeV) in this orbit can be observed. The results show a clear dependence on solar activity. At aroundL= 2, it is found that the variation in the radiation belt proton flux is controlled by both the flux of the galactic cosmic rays and the neutral density of the thermosphere. The former one is the source process of high‐energy charged particles in the inner radiation belt, and the latter is the loss process due to the Coulomb collision. It is also found that the influence of galactic cosmic ray fluctuations becomes smaller as theL‐value moves closer to 1.