Related by context. Frequent words. (Click for all words.) 70 auroras 66 auroral 65 Gamma ray bursts 64 aurora 63 substorms 61 X ray emission 61 geomagnetic storms 61 aurora borealis 60 solar flares 60 coronal mass ejections 59 interplanetary spacecraft 59 meteor showers 58 Earth magnetosphere 58 visible wavelengths 58 Saturn moon Enceladus 57 geomagnetic storm 57 magnetosphere 57 Crab Nebula 57 planetary nebula 57 gamma ray burst 57 geomagnetic 57 supernova explosion 57 GRBs 56 Eta Carinae 56 supernova explosions 56 Sunspots 56 volcanically active 55 meteors 55 Perseids 55 Leonids 55 lightning flashes 55 meteor shower 55 mid latitudes 55 Geminids 55 polar regions 55 gamma ray bursts 55 occultation 55 Orion Nebula 55 geomagnetic field 54 astrophysical 54 lunar eclipses 54 celestial object 54 Leonid meteor shower 54 astronomical objects 54 sunspot activity 54 Volcanic eruptions 54 unaided eye 54 supermoon 54 explosive eruptions 54 starbursts 54 sunspots 54 infrared wavelengths 53 Aurora Borealis 53 meteoroid 53 Jupiter Saturn 53 nebulae 53 Perseid meteor shower 53 sunspot cycle 53 ringed planet 53 distant galaxy 53 Kuiper belt 53 Andromeda Galaxy 53 constellation Perseus 52 Polar Regions 52 oscillations 52 convective 52 ionized gas 52 cosmic ray 52 annular eclipse 52 supernova remnants 52 perigee 52 microlensing 52 XMM Newton 52 astronomical observations 52 celestial objects 52 ionospheric 52 supernova remnant 51 geologically active 51 heliosphere 51 magnetar 51 ionosphere 51 Saturn moons 51 coronal mass ejection 51 planet orbits 51 nebula 51 cosmic rays 51 vortices 51 meteoroids 51 hydrological cycle 51 Galaxy Evolution 51 Voyager spacecraft 51 habitable planets 51 atmospheric circulation 51 volcanism 50 ecliptic 50 COROT 50 Enceladus 50 distant galaxies 50 infrasound 50 phenomena 50 sunrises