Articles Tagged "David Hathaway"

Solar physicists may have discovered why the Sun recently experienced a prolonged period of weak activity.

The most recent so-called "solar minimum" occurred in December 2008.

Its drawn-out nature extended the total length of the last solar cycle - the repeating cycle of the Sun's activity - to 12.6 years, making it the longest in almost 200 years.

During a solar minimum the Sun is less active, producing fewer sunspots and flares.

The new research suggests that the longer-than-expected period of weak activity may have been linked to changes in the way a hot soup of charged particles called plasma circulated in the Sun.

The study, conducted by Dr Mausumi Dikpati of the National Center for Atmospheric Research in Colorado and her US colleagues, is published in the journal Geophysical Research Letters.

The sun has cycles -- periods of high activity, when it has a lot of sunspots, and low activity, when things on the surface seem calm. NASA astronomer David Hathaway says activity is unusually low right now. A new solar observatory may shine light on the mystery.

Click source to listen to Radio Interview with David Hathaway and Ira Flatow (Host) and also read Transcript

The sun's temper ebbs and flows on what scientists had thought was a pretty predictable cycle, but lately our closest star has been acting up.

Typically, a few stormy years would knock out a satellite or two and maybe trip a power grid on Earth. Then a few years of quiet, and then back to the bad behavior. But an extremely long stretch of low activity in recent years has scientists baffled and scrambling for better forecasting models.

An expected minimum of solar activity, between 2008 and 2009, was unusually deep. And while the sun would normally ramp up activity by now, heading into its next cycle, the sun may be on the verge of a weak solar cycle instead, astronomers said at the 216th meeting of the American Astronomical Society in Miami last month.

We're witnessing something unlike anything we've seen in 100 years," said David Hathaway of NASA's Marshall Space Flight Center in Huntsville, Ala.

The sun's constant interaction with Earth makes it important for solar physicists to keep track of solar activity. Stormy periods can force special safety precautions by satellite operators and power grid managers, and astronauts can be put at risk from bursts of radiation spat out by solar storm. Scientists need to more reliably predict what's in store.

At the conference, four solar physicists presented four very different methods of measuring and tracking solar cycles.

Click source to read FULL report from Denise Chow

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Predicting the behavior of a sunspot cycle is fairly reliable once the cycle is well underway (about 3 years after the minimum in sunspot number occurs [see Hathaway, Wilson, and Reichmann Solar Physics; 151, 177 (1994)]). Prior to that time the predictions are less reliable but nonetheless equally as important. Planning for satellite orbits and space missions often require knowledge of solar activity levels years in advance.

A number of techniques are used to predict the amplitude of a cycle during the time near and before sunspot minimum. Relationships have been found between the size of the next cycle maximum and the length of the previous cycle, the level of activity at sunspot minimum, and the size of the previous cycle.

Among the most reliable techniques are those that use the measurements of changes in the Earth's magnetic field at, and before, sunspot minimum. These changes in the Earth's magnetic field are known to be caused by solar storms but the precise connections between them and future solar activity levels is still uncertain.

Satellite observations could improve forecasts of future solar cycles

Newly reported observations of gas flows on the solar surface may explain why the sun recently had such an extended case of the doldrums.

From 2008 through the first half of 2009, the sun had a puzzling dearth of sunspots, flares and other storms, extending the usual lull at the end of the 11-year solar activity cycle for an extra 15 months. Findings from the study, which relied on the orbiting Solar and Heliospheric Observatory, or SOHO, may also suggest a better way to forecast the intensity and duration of future solar cycles.

Better predictions could be critical because some solar outbursts can blast Earth with massive, magnetized clouds of charged particles capable of knocking out electrical power grids and harming communications satellites.

In the March 12 Science, David Hathaway of NASA’s Marshall Space Flight Center in Huntsville, Ala., and Lisa Rightmire of the University of Memphis in Tennessee analyzed 13 years of SOHO measurements that tracked the movement of ionized gas from the solar equator to the poles. The researchers found that the relatively slow gas movement, known as the meridional flow, sped up a few years before the last solar minimum began in 2008. What’s more, the flow was substantially faster than the speed at the previous solar minimum, a more typical and less extended downturn in solar activity some 11 years earlier.

Hathaway and Rightmire suggest that the faster meridional flow produced weaker magnetic fields at the sun’s poles, which extended the solar minimum.

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