{
  "$schema": "https://lumavik.org/api/v1/openapi.json",
  "endpoint": "https://lumavik.org/api/v1/cities.json",
  "description": "Aurora-viewing locations with their geographic latitude, their approximate corrected geomagnetic latitude, the Kp at which the modelled oval reaches overhead, the Kp at which a display becomes visible from the area, and how many hours of astronomical darkness each gets at midwinter and midsummer.",
  "count": 14,
  "provenance": "Geographic latitudes and the approximate corrected-geomagnetic ranges are the figures published in the city table on the page named in `source`. `kp_oval_overhead` is derived at build time from the corrected-geomagnetic midpoint through the same oval-edge table the site calculator uses, so the two can never drift apart.",
  "caveats": [
    "There are two different \"Kp you need\" numbers and confusing them is the most common error made with this data. `kp_oval_overhead` is the Kp at which the modelled auroral oval expands far enough for emission to be produced roughly above that location. `kp_visible_from_area` is the editorial estimate of when a display becomes worth going outside for from there, which is lower, because emission around 100 km up has a geometric horizon of about 1100 km and is routinely seen on the poleward horizon by people far outside the oval. Quote whichever you mean, and say which.",
    "Geomagnetic latitude here is the tilted-dipole approximation, not corrected geomagnetic (CGM) coordinates from the full IGRF model. The two differ by up to about two degrees in places, which near a threshold is one Kp step. Use it to decide roughly what a location needs, not to settle an argument about one degree.",
    "Darkness is computed from a low-precision solar declination series and is accurate to a few minutes of twilight time, which is far below what matters for planning a night. It ignores terrain, altitude, refraction near the horizon, artificial skyglow and cloud — and cloud is what actually ends most attempts."
  ],
  "field_notes": {
    "geographic_latitude": "Latitude on a map. On its own it predicts almost nothing about the aurora.",
    "corrected_geomagnetic_latitude": "Latitude relative to the geomagnetic pole, which is where the oval is centred. Minneapolis sits 11 degrees south of Edinburgh on a map and within two degrees of it magnetically; Moscow is level with Edinburgh on a map and five degrees below it magnetically. This column is the reason a map is a bad guide.",
    "kp_oval_overhead": "Null means even Kp 9 does not normally bring the modelled oval overhead there.",
    "kp_visible_from_area": "The page's own estimate, and the lower of the two numbers. See caveats.",
    "dark_hours_midwinter": "Hours with the sun more than 18 degrees below the horizon, at the local winter solstice. Zero in the summer row means the sky never gets properly dark — the season is closed regardless of Kp."
  },
  "related": {
    "thresholds": "https://lumavik.org/api/v1/visibility.json",
    "darkness": "https://lumavik.org/api/v1/darkness.json",
    "human_page": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/",
    "calculator": "https://lumavik.org/tools/geomagnetic-latitude-calculator/"
  },
  "licence": {
    "name": "CC BY 4.0",
    "url": "https://creativecommons.org/licenses/by/4.0/",
    "attribution": "Lumavik — https://lumavik.org",
    "note": "Free to reuse, including commercially, with a link back to the endpoint or the page a figure came from."
  },
  "cities": [
    {
      "city": "Tromsø",
      "country": "Norway",
      "hemisphere": "north",
      "geographic_latitude": 69.7,
      "corrected_geomagnetic_latitude": {
        "from": 67,
        "to": 69,
        "midpoint": 68,
        "approximate": true
      },
      "kp_oval_overhead": 0,
      "kp_visible_from_area": {
        "from": 1,
        "to": 3
      },
      "dark_hours_midwinter": 13.5,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Fairbanks",
      "country": "United States (Alaska)",
      "hemisphere": "north",
      "geographic_latitude": 64.8,
      "corrected_geomagnetic_latitude": {
        "from": 64,
        "to": 66,
        "midpoint": 65,
        "approximate": true
      },
      "kp_oval_overhead": 1,
      "kp_visible_from_area": {
        "from": 2,
        "to": 3
      },
      "dark_hours_midwinter": 13,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Reykjavik",
      "country": "Iceland",
      "hemisphere": "north",
      "geographic_latitude": 64.1,
      "corrected_geomagnetic_latitude": {
        "from": 63,
        "to": 65,
        "midpoint": 64,
        "approximate": true
      },
      "kp_oval_overhead": 2,
      "kp_visible_from_area": {
        "from": 2,
        "to": 3
      },
      "dark_hours_midwinter": 12.9,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Anchorage",
      "country": "United States (Alaska)",
      "hemisphere": "north",
      "geographic_latitude": 61.2,
      "corrected_geomagnetic_latitude": {
        "from": 61,
        "to": 63,
        "midpoint": 62,
        "approximate": true
      },
      "kp_oval_overhead": 3,
      "kp_visible_from_area": {
        "from": 3,
        "to": 4
      },
      "dark_hours_midwinter": 12.7,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Edinburgh",
      "country": "United Kingdom (Scotland)",
      "hemisphere": "north",
      "geographic_latitude": 56,
      "corrected_geomagnetic_latitude": {
        "from": 55,
        "to": 57,
        "midpoint": 56,
        "approximate": true
      },
      "kp_oval_overhead": 6,
      "kp_visible_from_area": {
        "from": 4,
        "to": 5
      },
      "dark_hours_midwinter": 12.3,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Moscow",
      "country": "Russia",
      "hemisphere": "north",
      "geographic_latitude": 55.8,
      "corrected_geomagnetic_latitude": {
        "from": 50,
        "to": 52,
        "midpoint": 51,
        "approximate": true
      },
      "kp_oval_overhead": 8,
      "kp_visible_from_area": {
        "from": 5,
        "to": 6
      },
      "dark_hours_midwinter": 12.3,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Seattle",
      "country": "United States (Washington)",
      "hemisphere": "north",
      "geographic_latitude": 47.6,
      "corrected_geomagnetic_latitude": {
        "from": 53,
        "to": 55,
        "midpoint": 54,
        "approximate": true
      },
      "kp_oval_overhead": 7,
      "kp_visible_from_area": {
        "from": 4,
        "to": 5
      },
      "dark_hours_midwinter": 11.8,
      "dark_hours_midsummer": 1.8,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Minneapolis",
      "country": "United States (Minnesota)",
      "hemisphere": "north",
      "geographic_latitude": 45,
      "corrected_geomagnetic_latitude": {
        "from": 53,
        "to": 55,
        "midpoint": 54,
        "approximate": true
      },
      "kp_oval_overhead": 7,
      "kp_visible_from_area": {
        "from": 4,
        "to": 5
      },
      "dark_hours_midwinter": 11.7,
      "dark_hours_midsummer": 3.3,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Chicago",
      "country": "United States (Illinois)",
      "hemisphere": "north",
      "geographic_latitude": 41.9,
      "corrected_geomagnetic_latitude": {
        "from": 49,
        "to": 51,
        "midpoint": 50,
        "approximate": true
      },
      "kp_oval_overhead": 9,
      "kp_visible_from_area": {
        "from": 5,
        "to": 6
      },
      "dark_hours_midwinter": 11.5,
      "dark_hours_midsummer": 4.4,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "New York City",
      "country": "United States (New York)",
      "hemisphere": "north",
      "geographic_latitude": 40.7,
      "corrected_geomagnetic_latitude": {
        "from": 47,
        "to": 49,
        "midpoint": 48,
        "approximate": true
      },
      "kp_oval_overhead": null,
      "kp_visible_from_area": {
        "from": 6,
        "to": 7
      },
      "dark_hours_midwinter": 11.4,
      "dark_hours_midsummer": 4.7,
      "source": "https://lumavik.org/skywatch/geomagnetic-latitude-and-aurora/"
    },
    {
      "city": "Ushuaia",
      "country": "Argentina",
      "hemisphere": "south",
      "geographic_latitude": -54.8,
      "corrected_geomagnetic_latitude": null,
      "kp_oval_overhead": null,
      "kp_visible_from_area": null,
      "dark_hours_midwinter": 12.2,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/aurora-australis-southern-lights/"
    },
    {
      "city": "Punta Arenas",
      "country": "Chile",
      "hemisphere": "south",
      "geographic_latitude": -53.2,
      "corrected_geomagnetic_latitude": null,
      "kp_oval_overhead": null,
      "kp_visible_from_area": null,
      "dark_hours_midwinter": 12.1,
      "dark_hours_midsummer": 0,
      "source": "https://lumavik.org/skywatch/aurora-australis-southern-lights/"
    },
    {
      "city": "Invercargill",
      "country": "New Zealand",
      "hemisphere": "south",
      "geographic_latitude": -46.4,
      "corrected_geomagnetic_latitude": null,
      "kp_oval_overhead": null,
      "kp_visible_from_area": null,
      "dark_hours_midwinter": 11.7,
      "dark_hours_midsummer": 2.6,
      "source": "https://lumavik.org/skywatch/aurora-australis-southern-lights/"
    },
    {
      "city": "Hobart",
      "country": "Australia (Tasmania)",
      "hemisphere": "south",
      "geographic_latitude": -42.9,
      "corrected_geomagnetic_latitude": null,
      "kp_oval_overhead": null,
      "kp_visible_from_area": null,
      "dark_hours_midwinter": 11.6,
      "dark_hours_midsummer": 4.1,
      "source": "https://lumavik.org/skywatch/aurora-australis-southern-lights/"
    }
  ]
}