Topline<\/p>\n
At 2:19 p.m. EDT on Monday, Sept. 22, 2025, the sun will cross the celestial equator heading south. That marks the fall equinox in the Northern Hemisphere \u2014 the first day of autumn \u2014 which means shorter days and longer nights are ahead. For aurora-watchers, however, it could mean something much more dramatic as Earth opens itself to potentially more intense geomagnetic storms \u2014 and more frequent Northern Lights<\/a>. Fittingly, a G1-rated geomagnetic storm is forecast, which could see auroras glimpsed in 14 U.S. states on Sunday, Sept. 21.<\/p>\n Northern lights erupt over a lake in Minnesota. <\/p>\n gettyKey Facts<\/p>\n The aurora borealis \u2014 the northern lights \u2014 occurs when charged particles from the sun accelerate down Earth\u2019s magnetic field lines and collide with molecules high in the atmosphere. That interaction produces shimmering curtains of predominantly green and red light.<\/p>\n Although it\u2019s the magnetic activity on the sun that is the root cause of auroras, scientists have long noticed a spike in geomagnetic disturbances around the equinoxes in March and September. This boost, known as the \u201cequinox effect,\u201d comes from geometry.<\/p>\n At an equinox, Earth\u2019s axis is side-on to the sun. The orientation of Earth\u2019s magnetic poles relative to the solar wind allows for a better alignment, making it easier for solar wind particles to slip through \u201ccracks\u201d in Earth\u2019s magnetosphere and spark auroras.<\/p>\n The combination of this geometry and longer nights in the wake of the equinox makes September one of the best times of year to see the Northern Lights.<\/p>\n A G1-rated geomagnetic storm is being forecast<\/a> by NOAA, with its \u201caurora viewline<\/a>\u201d crossing 14 U.S. states on Sunday, Sept. 21. <\/p>\n The Equinox Explained<\/p>\n Earth\u2019s tilted axis is side-on to the sun on Monday, producing almost equal amounts of daylight and darkness across the globe (the word \u201cequinox\u201d comes from Latin for \u201cequal night\u201d). It signals the start of astronomical fall in the Northern Hemisphere and spring in the Southern Hemisphere. The cause is Earth\u2019s axis, which is tilted 23.4 degrees relative to its orbit around the sun. That tilt causes the sun to appear to move north and south of the equator during the year. In June, the Northern Hemisphere is tilted toward the sun, meaning longer, hotter days, while in December, it’s tilted away, meaning shorter, colder days. The equinoxes in March and September are the transition points, when neither hemisphere leans toward the sun.<\/p>\n How The \u2018russell-Mcpherron Effect\u2019 Works<\/p>\n The scientific explanation for the uptick in aurora post-equinox is called the Russell-McPherron effect, proposed in the 1970s. It describes how, during equinoxes, Earth\u2019s tilt makes the magnetic field more likely to reconnect with the sun\u2019s magnetic field. When that happens, the flow of solar wind into Earth\u2019s magnetosphere intensifies. The result is brighter and more frequent auroral displays. That doesn\u2019t mean the lights suddenly appear everywhere. The effect increases the probability of auroras, but whether they\u2019re visible depends on solar activity. <\/p>\n When And To See The Northern Lights<\/p>\n Monday\u2019s equinox won\u2019t guarantee Northern Lights \u2014 strong solar activity is still required \u2014 but it does increase the odds. With Earth\u2019s magnetic field aligned, longer nights returning and the sun is near the peak of its 11-year solar cycle, sky-watchers should keep an eye on forecasts<\/a> and the aurora view line<\/a> from the National Oceanic and Atmospheric Administration\u2019s Space Weather Prediction Center, particularly in the two weeks before and after the equinox. <\/p>\n Further ReadingForbesNorthern Lights Update: Aurora Alert For Monday Night In 16 StatesBy <\/a>Forbes9 Places To Experience The Next Total Solar Eclipse A Year From TodayBy <\/a>ForbesMainland Europe To See First Total Eclipse Of The Sun Since 1999By <\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Topline At 2:19 p.m. EDT on Monday, Sept. 22, 2025, the sun will cross the celestial equator heading…\n","protected":false},"author":2,"featured_media":78070,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[270],"tags":[52542,52541,18,52544,52547,52540,52545,19,17,6952,52543,133,52546,52548,451],"class_list":{"0":"post-78069","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-space","8":"tag-aurora-borealis-september-2025","9":"tag-aurora-equinox-effect","10":"tag-eire","11":"tag-equinox-aurora-season","12":"tag-equinox-northern-lights","13":"tag-fall-equinox-2025","14":"tag-geomagnetic-storms-2025","15":"tag-ie","16":"tag-ireland","17":"tag-northern-lights-forecast","18":"tag-russell-mcpherron-effect","19":"tag-science","20":"tag-september-aurora-activity","21":"tag-solar-wind-aurora","22":"tag-space"},"share_on_mastodon":{"url":"","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/78069","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=78069"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/78069\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/78070"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=78069"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=78069"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=78069"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}