Weird Science

Aurora Borealis

Polish ver­sion is here

Few phe­no­mena in the sky can match the visual gran­deur of the auro­ras, or their pro­fo­und impact on our per­cep­tion of beauty. As we watch rib­bons of light slowly dan­cing across the night sky, we expe­rience not only aesthe­tic deli­ght but also a sense of tran­s­cen­dence. Many peo­ple describe this fee­ling as an inner calm cou­pled with intense curio­sity and awe. Yet true satis­fac­tion comes only with an under­stan­ding of what this spec­tacle actu­ally is.

Auro­ras, known in the Nor­thern Hemi­sphere as Aurora bore­a­lis or Nor­thern Lights and in the Sou­thern Hemi­sphere as Aurora austra­lis or Sou­thern Lights, can usu­ally be obse­rved near the polar circ­les — tho­ugh under favo­ra­ble atmo­sphe­ric con­di­tions, they occa­sio­nally appear aro­und the 50th paral­lel or, more rarely, in Medi­ter­ra­nean regions. This phe­no­me­non ori­gi­na­tes in the iono­sphere, rou­ghly one hun­dred kilo­me­ters above Earth’s sur­face, where the radia­tion belts inter­sect with the upper lay­ers of the atmo­sphere.

The Sun con­ti­nu­o­u­sly emits a stream of char­ged par­tic­les into space — what we call the solar wind. It is worth men­tio­ning solar fla­res here. This term refers to a set of phe­no­mena and phy­si­cal pro­ces­ses trig­ge­red by a sud­den rele­ase of a huge amo­unt of energy in the Sun’s atmo­sphere, cau­sed by the anni­hi­la­tion of magne­tic fields. Of course, the unle­a­shed energy does not appear out of nowhere — it was pre­vio­u­sly sto­red in the magne­tic fields of active regions on the Sun. During flare periods, the emis­sion of char­ged par­tic­les incre­a­ses signi­fi­can­tly: pro­tons, rea­ching ener­gies of up to about 1 GeV, and elec­trons of sli­gh­tly lower energy, enter Earth’s magne­tic field. Their move­ment is then direc­ted along magne­tic lines toward polar regions, exci­ting atoms of oxy­gen and nitro­gen and lea­ding to the emis­sion of radia­tion, inc­lu­ding that in the visi­ble range.

Solar par­tic­les with lower energy, emit­ted even without pro­mi­nent sun­spots, are also cap­tu­red by the radia­tion belts, tho­ugh they do not pro­duce such spec­ta­cu­lar effects. Howe­ver, when intense solar storms occur, the poten­tial dif­fe­rence in the magne­to­sphere can reach tens of kilo­volts, which ampli­fies cur­rent flows. Auro­ras are most fre­qu­en­tly obse­rved just before mid­ni­ght, but they can some­ti­mes be seen even during the day, as well as at mid­dle and low lati­tu­des, espe­cially fol­lo­wing strong solar fla­res.

Obse­rva­tions

May 11, 2024 – Jaworzno (Poland)
Con­di­tions: sub­ur­ban

The first half of May 2024 tur­ned out to be a record-bre­a­king period in terms of solar acti­vity. In total, the Sun emit­ted eigh­teen class X fla­res that month — X being the highest class in terms of X-ray inten­sity. High solar acti­vity began on May 3, but ear­lier fla­res were merely a pre­lude to the whole series that took place from May 8 to 15 of that month. There was an X5.8 flare, which at that time was the second stron­gest in that solar acti­vity cycle. It comes as no sur­prise, then, that during those days — par­ti­cu­larly from May 10 to 12 — exten­sive auro­ras were visi­ble, easily obse­rved even in sou­thern Poland, which I mana­ged to pho­to­graph (Phot.1).

Ilustracja: Phot. 1 - without labels

Phot. 1 - without labels

Ilustracja: Phot. 1 - with labels

Phot. 1 - with labels

Due to their forms, a variety of aurora types are distin­gu­i­shed: bands, arcs, cur­ta­ins, rays, crowns, and others. Emis­sions can be obse­rved in blue, green, yel­low, and red hues, and very often in white. The color of the phe­no­me­non stems from dif­fe­ring inten­si­ties of emis­sion lines, depen­ding on the type of gas exci­ted and the alti­tude at which the display occurs. Oxy­gen emits red and green light, while nitro­gen glows in pur­plish sha­des. Com­bi­na­tions of these gases, along with con­tri­bu­tions from hydro­gen and helium, can yield other colors as well.

Fur­ther rea­dings:

Marek Ples

Aa