The solar wind data displayed within the app is retrieved from the Space Weather Prediction Center (SWPC) every minute. While it is normally reliable to retrieve data from SWPC, there are times when data is unavailable for a variety or reasons (bad data connection, loss of communication with the satellite, server downtimes, etc.). In cases where data is unavailable for certain timeframes, users will see “No Data for This Period” displayed during the respective timeframe.
The top portion of the solar wind display shows the table of solar wind data expected over the next hour. This includes the Bz, Bt, particle density, solar wind speed, and the hemispheric power index (HPI). Below this is a SWPC status indicator for the solar wind, Kp data, and HPI data. Green indicates data is flowing as expected, yellow indicates data may be old or degraded, and red means data is not being received. These are useful to know if the data stream may be dropping out soon.
Immediately below the SWPC status is the legend. This legend helps you read the data in the solar wind table by indicating whether or not values are poor (green), fair (yellow), or good (red). A common question for the data is, why is red good? Solar data is color coded differently than one would think. Normally, green is good and red is bad. In the case of solar activity, it is color coded based on the level of severity. Thus, green is less severe and red is more severe. The values in the legend indicate, based on observations around 60N, what is considered in these severity ranges. These are basic guidelines and may vary slightly depending on your exactly location.
Immediately below the legend is an aurora probability. This probability is based on the solar wind data and the OVATION model output provided by SWPC. It is generally good to within about 10-15 minutes of arc and aurora activity being visible.
Below the probability block is the Kp information. This includes the currently observed Kp, the next hour’s forecasted maximum value, and the next three days worth of forecast information from SWPC. The Kp values are check every minute and the 3-day forecast is updated by SWPC once per day.
The last block of information on the main solar wind screen is the SWPC event forecast. These are the probabilities of C, X, and M-class flares as well as proton events. C-class flares are the most common flares the sun produces which can cause noticeable effects on Earth. An M-class flare is 10 times stronger than a C-class and an X-class flare is 10 times stronger than an M-class. An X9 flare is the largest, most powerful flare SWPC measures from the Sun. For aurora activity, flares are important. Flares eject material away from the Sun and, at times, can produce coronal mass ejections (CMEs). When a CME occurs, large amounts of solar material escape the gravity of the Sun and are projected outward into the solar system. These events can, and usually do, greatly enhance aurora activity here on Earth. Proton events do not, themselves, enhance aurora activity but can be an indicator of other solar activity of interest to keeping an eye out for the aurora. You can read more about solar flares here and proton events here.
So, how do you use all of this to determine if it is good to chase? We are generally looking for most of the solar wind data to be in the fair to good range. The more fair and good the data, the greater the chances of seeing aurora activity. Two important factors to keep an eye on are the interplanetary Bz and HPI values. Generally, the more negative (south) the Bz value is and the higher the HPI value is, the better your chances are of seeing aurora activity. The HPI value required for your location may be high, so keep an eye out on data and use the probability block to determine if it will be possible to see activity soon. You can jump to the guide page on Bz here or HPI here if you would like to read more about those now.