The Superflare SOL2017-09-06: from submm to mid-IR

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Revision as of 14:49, 17 March 2021

Introduction

Solar flares famously emit radiation across all electromagnetic wave bands, but we first accessed the mid-infrared (10 μm or 30 THz) only recently (Ref. [1]). The M2-class flare SOL2012-03-13T17 showed up clearly in the mid-IR, and also as a white-light flare that could be interpreted as optically thin thermal emission from precipitating electrons, as described via numerical models. Since that time several other mid-IR flares have been reported, and now we describe the remarkable X9.3 "superflare" SOL2017-09-06T12.

The superflare was one of a series of major events occurring in active region NOAA 12673, and the observations described here include mm-wave (212 and 405 GHz) observations as well as novel mid-IR imaging at 17 arc s resolution.

Observations

The mid-IR observations were obtained from a 15-cm telescope mounted on the roof of the CRAAM laboratory in the heart of São Paulo, Brazil (Ref. [2]). This Hale-type coelostat now feeds an uncooled microbolometer array with digital output at 320x240 pixels, matching the diffraction limit at 17 arc sec (Figure 1).

Figure 1: The Hale-type coelostat installed at the rooftop of CRAAM, in the center of São Paulo city, to project the solar radiation into the 30 THz telescope into the laboratory for imaging at H&alpha$ as well as the mid-IR.

References

[1] Kaufmann 2013

[2] Kudaka 2015