科研之友
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摘要
The ion tails of bright comets have long been considered as a natural tracers of the solar wind (SW) near these objects. Studies of comets and their ion tails allow inexpensive monitoring of key SW structures in the inner heliosphere, much of which is otherwise only accessible by in situ SW spacecraft measurements. Here, we present a novel technique to mine the rich archive of amateur, professional and spacecraft observations of cometary ion tails. To demonstrate this, we focus on Near‐Sun comet C/2011 L4 (Pan‐STARRS) during Carrington Rotations (CR) 2134 and 2135 and comet C/2013 R1 (Lovejoy) during CR 2118. We outline the technique’s shortcomings, including its geometric limitations, and present a catalog of radial SW velocities derived in the near‐comet environment and information on the heliospheric conditions inferred from the measured SW. Complementary measurements, derived from folding ion rays and a velocity profile map built from consecutive images, are provided as an alternative means of quantifying the SW ‐cometary ionosphere interaction. We find that comets are generally good indicators of SW structure, but the quality of the results is strongly dependent on the observing geometry.(#br)Plain Language Summary(#br)Comets, as they move through the inner solar system, can be considered as natural laboratories of the solar wind (SW). The SW is a continuous stream of fast charged particles that carries with it a remnant of the solar magnetic field into the solar system. Sourcing images from the internet and astrophotographers, we developed a new technique and the software to measure the SW speed in the comet’s orbital plane by using the ion tails of comets. The ion tail behaves similarly to a transparent windsock and indicates the direction of the SW. This allowed us to create a snapshot map of the SW variations along a comet’s orbit when it is close to the Sun. We also outline the reliability and the limitations of the technique and a catalog of SW velocities from comets C/2011 L4 (Pan‐STARRS) and C/2013 R1 (Lovejoy). We find that with the right geometry, comets are good and efficient probes of the SW. This catalog of speeds will help us to better understand the three‐dimensional structure and variability of the SW.(#br)Key Points(#br)Multi‐point multi‐latitudinal solar wind (SW) velocities can be derived from cometary ion tails(#br)Images acquired from observatories, STEREO B provide comparable results to amateur astronomers(#br)Results validated against 3D MHD models offer snapshots of the SW structure
