Sign up for our daily briefing

Make your busy days simpler with Axios AM/PM. Catch up on what's new and why it matters in just 5 minutes.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Stay on top of the latest market trends

Subscribe to Axios Markets for the latest market trends and economic insights. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Sports news worthy of your time

Binge on the stats and stories that drive the sports world with Axios Sports. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Tech news worthy of your time

Get our smart take on technology from the Valley and D.C. with Axios Login. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Get the inside stories

Get an insider's guide to the new White House with Axios Sneak Peek. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Denver news?

Get a daily digest of the most important stories affecting your hometown with Axios Denver

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Des Moines news?

Get a daily digest of the most important stories affecting your hometown with Axios Des Moines

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Twin Cities news?

Get a daily digest of the most important stories affecting your hometown with Axios Twin Cities

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Tampa Bay news?

Get a daily digest of the most important stories affecting your hometown with Axios Tampa Bay

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Charlotte news?

Get a daily digest of the most important stories affecting your hometown with Axios Charlotte

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Our Expert Voices conversation about the 2017 solar eclipse.

The solar corona — the outer atmosphere of the Sun that is revealed so spectacularly during a total solar eclipse — is one of the great mysteries in space science. The biggest puzzle of all is its extreme temperature of several million degrees. Why is the corona so hot when the solar surface below is a comparatively paltry 6,000 degrees?

Most solar physicists believe the primary source of the heat is stressed magnetic fields that permeate the corona and impulsively release pent up energy when the fields reach their breaking point. Occasionally this produces giant explosions called solar flares and coronal mass ejections. But much smaller nanoflares are happening all the time — about a million per second across the Sun — each equivalent to the detonation of a 50 megaton hydrogen bomb.

Why it matters: The corona produces large quantities of X-ray and ultra-violet radiation that are absorbed in Earth's upper atmosphere. Variations in radiation affect the propagation of radio signals, which adversely affects communication, navigation, surveillance, and precision weapons guidance systems. The upcoming solar eclipse affords us a rare view of the Sun's atmosphere and a chance to study how it gives rise to nanoflares so that we can improve space weather forecasts.

Other voices in the conversation:

Go deeper

Neera Tanden withdraws nomination for Office of Management and Budget director

Neera Tanden testifying before the Senate Budget Committee in Washington, D.C., in February 2021. Photo: Anna Moneymaker/The New York Times/Bloomberg via Getty Images

Neera Tanden withdrew her name from nomination to lead the Office of Management and Budget after several senators voiced opposition and concern about her qualifications and past combative tweets, President Biden announced Tuesday.

Why it matters: Tanden’s decision to pull her nomination marks Biden's first setback in filling out his Cabinet with a thin Democratic majority in the Senate.

What's ahead for the newest female CEOs

Jane Fraser (L) and Rosalind Brewer. Photos: Jason Redmond/AFP via Getty Images; Rodrigo Capote/Bloomberg via Getty Images.

The number of women at the helm of America’s biggest companies pales in comparison to men, but is newly growing — and their tasks are huge.

What's going on: Jane Fraser took over at Citigroup this week, the first woman to ever lead a major U.S. bank. Rosalind Brewer will take the reins at Walgreens in the coming weeks (March 15) — a company that's been run by white men for more than a century.

3 hours ago - Health

Biden says U.S. will have enough vaccines for 300 million adults by end of May

President Biden. Photo: Anna Moneymaker-Pool/Getty Images

President Biden on Tuesday said that ramped-up coronavirus vaccine production will provide enough doses for 300 million Americans by the end May.

Why it matters: That's two months sooner than Biden's previous promise of enough vaccines for all American adults by the end of July.