Auroras Now! Auroral nowcasting service for hotels, amateur astronomers, and general public Kauristie, K.1), Mälkki, A.1), Ketola, A.1), Nevanlinna, H.1), Raita, T.2), and Blanco, A.1) 1) Finnish Meteorological institute 2) University of Oulu

Abstract Auroras Now! is an auroral nowcasting system utilizing magnetic field and all-sky camera observations and cloudiness predictions made in Finland. The service includes three parts: a set of public web-pages, a private service customized for two hotels in Lapland, and a SMS-service for the largest Finnish association of amateur astronomers. The public part concentrates especially to strong space weather events, while the hotel service is adjusted to monitor also moderate activity occurring within the standard auroral zone. The core element of Auroras now! is a robust auroral alarm system which follows the hourly maximum of dH/dt and issues an alert if the pre- defined threshold value gets exceeded. Daytime alerts often serve as reliable “predictions” for the forthcoming night's activity.

User feedback The hotel system is usable (no technical problems and no clouds) for 70% of the time and it can characterize the auroral occurrence and intensity of the forthcoming or on-going auroral activity in 80% of the cases. Hotel clients are happy with the performance. However, evaluating the financial benefit is difficult. The marketing value is important, but making a connection between sales and this service is not obvious. The SMS-service provides updates for the amateur astromers also in the wilderness. The time resolution could be higher, e.g.10 min. General public: web-site hits correlate with magnetic activity. Daily average , peak values near 500 (March 11, 2004). The number of customers of the freely available alerts has increased from 160 to 490.

Prospective for improvements The coverage of auroral observations will be improved by adding one more ASC to the system (KEV, North-eastern Lapland) Short-term predictions based on solar observations could be integrated to the system. Collaboration with the SIDC SDA (PRESTO) would be the most reasonable way to do this improvement. If prediction cababilities are added also warnings about their caveats must be clearly announced. This is a challenge especially for the hotel service where the available space is limited. The hotel customers do not necessarily have much background knowledge and their tolerance for failures is low. The hotel service would still need efficient marketing to get more customers and a 24/7 helpdesk service to avoid annoying breaks during the time of peak usage (which typically is outside the normal office time).

Auroral observations by MIRACLE ● Auroral latitudes: Sodankylä Geophysical Observatory (SOD, MLAT ~ 64) ● Sub-auroral latitudes: Nurmijärvi Geophysical (NUR, MLAT ~ 57) ● SOD: magnetic field data and auroral images; NUR: magnetic field data ● Only stations with fixed Internet- connection can be used ● Digital auroral images: – nm – updated once per minute – spatial resolution a few km ● Cloudiness predictions from FMI Regional Weather Service at Rovaniemi (the pink dot in the map)

Public web-pages (1/2) ● ● Dynamic parts: – hourly updated bar plots of max(dH/dt) – real-time auroral images during dark hours ● Archives: – previous night activity: Magnetograms and ASC keograms from other MIRACLE stations – cumulative records of max(dH/dt) values – Evaluation of the auroral alarm system

Public web-pages (2/2) ● Background information: – auroras and space weather – prediction of auroral activity – statistics about auroras – description of the ESA pilot project ● Expert opinions: – weekly space weather reports – replies to the questions from feedback forms

Hotel service (1/2) ● A sequence of three pages: (i) general info page from sun rise to noon, (ii) warm-up page from noon to sun set, and (iii) on-line page during dark hours. ● Appearance adjusted to be suitable for hotel-TV displays

Hotel service (2/2) ● Dynamic parts: Hourly updated magnetic activity monitor (1), Cloudiness predictions (2), near real-time ASC raw image (3), ASC image on map (4), and a recently acquired auroral animation (5). 43

SMS service (1/2) ● Customer: URSA, the largest Finnish association for amateur astronomers ● The service generates messages to the URSA system for rare optical phenomena. ● Santa Margarita Ltd provides a web-interface for adjusting the number of SMS-messages. The client can choose between the three different activity levels and geographic areas (northern and/or southern Finland). ● Price for the Santa Margarita service: Yearly payment 24 euros + 15 cnt per message.

SMS service (2/2) ● Message must give a characterization of the activity (or occurrence probability) in a scale of three levels: slightly enhanced, clearly enhanced and exceptionally strong activity ● The system makes also discrimination between the first alarms (either the first event of the night or change in the activity level) and updating alarms (activity continues on the same level). ● Instead of individual max(dH/Dt) values magnetic activity events are analysed ● Magnetic Disturbance Level (MDL) values depend both on the duration and peak dH/dt of the event ● MDL values are used also in the hotel service Yes No Read max (dH/dT) Above threshold? Continuation of an on going event? Start the record for a new event Update the record of the ongoing event Define the disturbance level and the label (first or update) for the alert Define the disturbance level and the label (first or update) for the alert Send the alert and save the disturbance level

Halloween storm: dH/dt

Halloween storm:dH/dT

Halloween storm: Auroras

Halloween storm as observed by Auroras Now! ● Red bars: increased probability to see auroras (alarm on). Threshold at NUR (southern Finland) 0.3 nT/s and at SOD (northern Finland) 0.5 nT/s. ● Time of continuous alarm started at SOD on Oct 28 at 16 UT and at NUR on Oct 29 at 07 UT. ● The highest bars Oct 30: at SOD at 20 UT (~18 nT/s) and at NUR at 22 UT (~14 nT/s) (c.f. the Malmö blackout took place on Oct 30 at 2007 UT) ● Activity continued at SOD during night time until the morning of Nov 4. Both SOD and NUR recorded a short re-intensification on Nov 4 during UT. ● Brightest auroras at SOD during Oct UT and from Oct UT to Oct UT. Cloudy sky from the evening of Oct 30 to morning Nov 2.